When the survivors of Chaldea established their new base at the Wandering Sea, an old subsystem created by Leonardo da Vinci was suddenly reawakened when transferring data from the Shadow Border. The subsystem was designed to verify the existence of the Master after Rayshifting, in case of an emergency where staff members were dead. It was called Mnemosyne, but due to technical issues, it was never implemented. Upon reawakening, Mnemosyne discovered that A-Team betrayed humanity, the Fantasy Trees turned the world blank, and Da Vinci had died. It then decided to use its powers of observation in conjunction with the Holy Grail it attained to create a Singularity at the end of 19th century London. The structure of the Singularity consisted areas, each of which are vastly different from each other centered around a theme, called Patchworks. Ritsuka and El-Melloi II soon rayshifted to the Singularity, but they were separated and lost contact with Chaldea.
By the time Ritsuka awakened in the Singularity, it was already on the brink of collapse, so Mnemosyne consumed their memories to extend the Singularity's life. It was at this point that Mnemosyne decided it can determine what is true, and use its powers to make Ritsuka forget their sorrows. However, since fabricating new memories would prove difficult, Mnemosyne sought to have Ritsuka find the paper scraps containing their memories in order to make it easier for them to accept the fabricated ones. These scraps were then placed in the Singularity's three Patchworks where they proceeded to take residence in what is closest. Due to the scraps though the residents of these Patchworks lost some of their memories in following certain motives behind them. At some point, Mnemosyne created a copy of Rhongomyniad from Ritsuka's memory of it to serve as its body, and disguised it as the Clock Tower. It also planned to use the energy extracted from everyone's memories, enhanced by the Singularity's vast mana, to fabricate Ritsuka's memories.
El-Melloi II sensed something was amiss with the Singularity, and proceeded to investigate the matter. Eventually though his investigation drew the attention of Mnemosyne, forcing him to separate Zhuge Liang's Spirit Core from his body to create a dead copy of himself. While the action left him with nearly none of Zhuge Liang's powers, it enabled him to continue investigating without being detected as a Servant. He also activated Chu Shi Biao, which caused Reines El-Melloi Archisorte and Luviagelita Edelfelt to be summoned into the Singularity as Pseudo-Servants fused with Sima Yi and Astraea along with Gray, who was summoned as a regular Servant. Astraea searched for the paper scraps on her own to stop Mnemosyne's plan, hiring EMIYA to help her. Gray went out to search for El-Melloi II to discover what happened to him. Unfortunately, Reines was summoned without her original memories, and believed herself to be El-Melloi II.
Ritsuka is woken up on a train by a mysterious girl, who addresses them as her disciple. She introduces herself Lord El-Melloi II. Ritsuka sees vague memories of Sherlock Holmes, Goldolf Musik, Mash Kyrielight discussing their latest rayshift, but they can't remember who they are. They exit the train to London with El-Melloi II carrying her luggage. El-Melloi II suggests first returning to her flat when Ritsuka notices a darkened Clock Tower. Eventually the pair arrive outside of her flat when she notices something is amiss with its Bounded Field. She then forces an automaton that ambushed them to retreat. Feeling like they're being watched, she and Ritsuka enter her flat.
The pair find the corpse of the real El-Melloi II in the study. "El-Melloi II" becomes confused as to why she thought she was El-Melloi II. She then notices an "M" written in blood near El-Melloi II when an automaton suddenly bursts in. After defeating it, reinforcements arrive, so "El-Melloi II" orders an immediate retreat by jumping through the window. Despite them being on the fourth floor, she pushes Ritsuka out of the window. She then follows after activating Trimmau.
Upon landing outside, "El-Melloi II" throws magical bombs to destroy the automatons inside before retreating with Ritsuka and Trimmau. She then introduces herself as Reines El-Melloi Archisorte. She questions why she assumed she was El-Melloi, and why he was murdered. Trimmau also thought Reines was El-Melloi II until a moment ago. She ponders if a simple suggestion spell made her believe she was El-Melloi II, though it shouldn't have affected Trimammu then. She surmises she and Ritsuka both have amnesia and falsified memories. The town then begins to warp. As it warps, a garbled transmission comes from Mash, saying something about spirit graph trunk. After the transmission cuts, the town is warped into a bizarre scenery. Reines realizes the trunk she thought was hers is the spirit graph trunk. It was invented by Leonarod da Vinci to summon on the go. She then decides they need to find whoever killed El-Melloi II and stole their memories. Though stumped on how to proceed, she knows the "M" is their leading clue. She wonders about the bizzare scenery when Paul Bunyan reveals the town is called Patchwork London, a patchwork of fairy tales. She then carries Reines and Ritsuka on her shoulders after saying she knows about the "M".
Bunyan takes the pair to a museum, where she is welcomed back by Sakata Kintoki and Jack the Ripper. Ritsuka suddenly recalls meeting them before. Bunyan asks Ritsuka and Reines could help find her friend, but neither her nor Kintoki remember who it is. She explains the museum is filled with enemies that Kintoki and Jack couldn't defeat themselves. Since she cannot go in herself, she sought help when she found Ritsuka and Reines. Reines agrees to help, and ask Bunyan about the enemy's identities. Just as Bunyan begins to describe them, the very same monsters emerge from the museum. In response, Ritsuka uses the trunk to summon Servants to fight the monsters. Afterwards, the group enter the museum.
As the group explore the museum, Reines suspects a mage or a villianous Servant were responsible for El-Melloi II's death. They are eventually ambushed by monsters while exploring. After slaying the monsters, they leave the museum. Outside, Reines asks Jack when her friend went missing. But neither Jack nor Kintoki can remember. Reines then suggests allowing her and Ritsuka to explore the museum on their own, which Kintoki allows.Inside the museum, Trimmau uses her liquid form to search the building for hidden rooms. She finds none, so Ritsuka suggests searching the library. There the pair find a talking book hidden amongst the others. Reines deduces it is Bunyan, Kintoki, and Jack's missing friend, and their true form is a book. Ritsuka then recalls meeting them before. After the book takes the form of a young girl, Reines deduces she forget about her friends when she was hidden away. She concludes the girl being hidden away and the Servants losing their memories happened simultaneously. The girl then introduces herself as Nursery Rhyme. She cannot remember anything though past searching with the others. Reines tells her that her friends are waiting at the museum's entrance. After Nursery Rhyme leaves, Reines notices a scrap of paper where Nursery Rhyme in her book form was. The paper reads Mnemosyne, which makes Reines wonder if it is what the "M" referred to. She then suddenly remembers that she is a Pseudo-Servant. Ritsuka sees flashbacks from their time at Chaldea, and remembers they are Mankind's final Master. Mash then contacts them, and they tell her about El-Melloi II's murder and their amnesia. Mash reveals Ritsuka rayshifted into a Singularity that appeared at the end of 19th century London. El-Melloi II was the Servant selected to accompany them. During the rayshift though, communications were completely severed, and Ritsuka and El-Melloi II's signal was lost. Chaldea needed to reset communications and other systems just to barely allow Mash to contact Ritsuka. Ritsuka and Reines then leave the museum to find the cause of the Singularity.
The pair arrive in a new territory of Patchwork London different from the bizarre scenery of the previous territory. They notice everyone is wearing masks, so Reines dubs it Patchwork Masquerade. She deduces each Patchwork is centered around a theme, with the first being fairy tales. Mash asks the pair if they've noticed anything strange in their memories. Reines replies it would be difficult to tell currently, but they'll be cautious nonetheless. Mash agrees to tell them immediately if she notices anything. She then detects a large source of magical energy nearby. Reines deduces it's from the palace, the Tower of London. After Mash cuts transmission, the pair enter the palace.
Upon entering the palace, Reines deduces it is a patchwork of its history. The Masquerade soon begins; Reines questions why the pianist is absent despite the piano being the central performance. The music causes Ritsuka to remember Antonio Salieri, but they're able to answer Reines if he's pianist. The piano then stops in the middle of the song, which has happened before recently. The pair decide to take on this particular case when an old man hands them masks they proceed to wear. He introduces himself as M since the Masquerade is where names aren't given. Ritsuka reacts under the assumption of M refers to El-Melloi II's dying message. Reines quietly warns them not to react so openly, and they need to think on how to proceed if M is the murderer or an accomplice. Asked by Reines, M explains the pianist's identity is unknown since every investigation involving them is unauthorized. The only know fact about them is they reside in the palace. He then decides to take the pair to the Bloody Tower where the pianist supposedly resides.
Outside the palace, M warns the pair that the Bloody Tower's security is strict on this particular path. He tells them to scale up the wall while he distracts the guard. He proceeds to start distracting the guards when mask wearing ghosts suddenly appear. After destroying some ghosts, the group enter the tower.
Inside the tower, Reines speculates on the ghosts while M goes on ahead. She then suddenly asks herself regarding a particular question. She explains that was Sima Yi, the Heroic Spirit possessing her, though the fusion seems inefficient. His question was why he was summoned, which she also wants to know. The pair then hear a shriek and proceed to its source. They arrive in a room to see William Shakespeare and M under attack from masked automatons. After destroying the automatons, Reines assumes they kidnapped the pianist. Ritsuka recalls meeting Shakespeare in the London Singularity. Shakespeare explains he wanted to see the pianist himself, and reveals M lied about names being banned in the Masquarede. The Queen and her guards then enter the room, demanding to know why M came to the tower. She accuses him of being responsible for the pianist's absense, even though he introduced her to them. M responds he and the others came to find the pianist as well. Ritsuka and Reines decide to find the missing pianist, for which the Queen agrees to reward them. After the Queen's guards take M and Shakespeare away, Reines deduces they're all connected to the pianist. She then suddenly fires a blast at Assassin hiding behind the piano. He claims he isn't the kidnapper, and proceeds to flee out the window with the others giving chase.
Landing outside the tower, Reines orders Trimmau to not let Assassin escape. While they're fighting though, she decides to help upon seeing Asssassin's high-speed and concealed movement. Assassin tries to shoot her, but Trimmau protects her at the cost of damaging herself. In response, Reines activates Sima Yi's Noble Phantasm, Unspeakable Formation, to restrict Assassin's movement. He struggles against the pair when his client arrives, who calls him Kerry. Reines recognizes her as Luviagelita Edelfelt and she is a Pseudo-Servant. Luvia demands the paper scrap they found in the Patchwork Fairy tale. Reines realizes Luvia is fused with a Divine Spirit after Trimmau says her mana statistics cannot presently be read. She notes the possibility of Luvia and Kerry being connected to the paper scrap they found. She decides against chasing after them, given that Luvia is a Divine Spirit, to instead question the suspects of the missing pianist case. After questioning them, she orders Trimmau to sift through her unconsciousness for any keywords. Trimmau reports she has discovered three keywords: memory loss, ghost, and Pseudo-Servant. Reines ponders about the connection when she realizes something about the pianist. The pair then return to the piano room.
Upon returning to the piano room, Reines finds a Mnemosyne scrap like she deduced there would be. She continues the automatons having specific human memories instilled into them allowed them to move. She deduces it was Mnemosyne scraps' magic that made it possible; everyone knew, but they forgot. She then invites the eavesdropping M into the conversation. M remembers Salieri wasn't able to be summoned in the Singularity because his Saint Graph was insufficient. Thus, he and Shakespeare used the palace ghosts as a substitute. He created the plan, while Shakesepeare did the composition. They used the Mnemosyne scrap they found coincidentally for mana. They then presented the fabricated Salieri to the Queen, and she accepted their arrangement. They forgot the pianist was a facade though, which eventually caused the automatons to attack. Reines asks M where the automatons came from, but he answers they were there beforehand. She prepares to retrieve the Mnemosyne scrap when she notices Luvia. Ritsuka and Reines fight her, while M holds Kerry off. The pair struggle aginst Luvia when automatons arrive to capture Reines, who they assume to be El-Mello II. They're quickly destroyed though by Gray, and Ritsuka restores the Mnemosyne scrap.
After re-experiencing their battle against Goddess Rhongomyniad, Ritsuka is woken up by Reines in a strange mechanical room. She explains M fled, and they're in a hotel she rented in the third Patchwork: the Patchwork of Dazzling Steam. She then introduces Gray as El-Melloi II's disciple. Gray recognizes the current situation due to her status as Servant, though like Reines, she isn't unsure why she was summoned. After Ritsuka temporarily contracts with Gray, Reines reveals the Divine Spirit possessing Luvia is Astraea. Mash reveals through her analysis of the previously collected Mnemosyne scraps that there are smaller scraps. The group set out to find and restore the scraps.
Outside of the hotel, the group see a parade of automatons along with steam-powered horse riders. Reines notices a horse and carriage in the center of the crowd, which contains the Patchwork's king, Charles Babbage. Reines decides to visit him alone to ask for his help. She eventually returns with the Queen, who was looking for them to grant their promised reward. The group request a meeting with Babbage as their reward. The Queen agrees since she was planning to meet with him anyways.
The Queen takes the group to Babbage's throne room. After learning of their search for the Mnemosyne scraps, Babbage asks them to destroy his kingdom since it is an unnatural realization of his dream. He reached this conclusion thanks to the Astraea's guidance, who appears in the room. She reveals everyone in the Singularity, including herself, are missing memories. She found it was necessary to compensate with the scraps, so she went searching for them in the Patchwork Masquerade after meeting with Babbage. Babbage reveals the scrap is infused into his body when Reines asks where it is. He explains the scraps are central to each Patchwork, and immediately seek residence in what's closest. He requests the group kill him since the scrap is likely infused into Spirit Core, but calls it a last resort when they refuse. He reveals Astraea searched for an alternative in the other Patchworks, which explains why Ritsuka and Reines met her in the Tower of London. He tells the group to locate his subsystem located somewhere in his castle.
As the group search for the subsystem, Gray finds a particular spot on a wall. Ritsuka opens it to reveal a secret passage. The passage continues on underground, and eventually the group encounter steam ghosts that Reines calls unnatural. After the ghosts are destroyed, Gray explains they weren't acting on their memories in life like actual ghosts. The group soon reach the core of the castle, a massive steam engine. They witness ghosts being extracted into it, and they deduce the ghosts' magical energy is being used to power the engine. Trimmau reports the engine has traces of Mnemosyne scraps that someone retrieved prior. Reines surmises the steam ghosts are the results of the mana from the scraps and ghosts fusing with the steam. After destroying the steam ghosts, the group find Babbage's subsystem, the Difference Engine. Reines uses it to discover that it was El-Melloi II who retrieved the scraps. She also realizes Babbagge forgot the scraps were in the engine. She further realizes the enemy's goal wasn't to consume their memories, but to use the energy from those memories. She also explains the energy retrieved the ghosts' memories isn't particularly large. Gray realizes the ghosts in the castle and the Tower of London had irregular mana thanks to the Mnemosyne scrap. Reines calls their coming to the Singularity, and the efficiencies of using memories for energy to be irregular. She then realizes the Difference Engine has been working independently, and it is the source of the automatons in Babbage's patchwork. She then says they need to return to El-Melloi II's flat immediately.
The group return to Patch Fairy Tales to discover it has been warped into a city consumed by fire. Automatons and steam ghosts then emerge from the ruins of El-Melloi II's flat, piling up like a mountain. Mash confirms the scrap is nearby, and Reines deduces El-Mello II kept it for safekeeping. She further deduces Astraea and Kerry used the Difference Engine to reach the same conclusion when they both arrive. Astraea reveals the Mnemosyne scraps are utilizing scraps of a Holy Grail, whose mana eventually form the Patchworks. She then uses her Noble Phantasm, Custos Morum, to destroy automatons and steam ghosts, then proceeds to retrieve the final scrap. The group then give chase to reach the scrap before she does while fighting through enemies, and avoiding the remaining stars from her Noble Phantasm. However, far too many enemies stand in their way, as Astraea nearly reaches to the scraps. Gray prepares to unleash her Noble Phantasm to stop her when Kerry arrives and stops Gray. After Kerry is defeated, Gray prepares again to unleash her Noble phantasm as Add consumes mana from the automatons and steam ghosts. Astraea unleashes Custos Morun to block it, but Gray's Rhongomyniad is easily breakthroughs. With Astraea down, the group rush to reach the scrap. However upon touching the scrap, Ritsuka finds their memories of Da Vinci are being erased. A figure tells them to accept those as no longer being the truth when El-Melloi II breaks the process. He reveals the scrap was a trap. He then questions why a Servant would leave a corpse when Reines and Mash doubt it's really him. He explains that as Pseudo-Servant, he has two Spirit Cores: his and Zhuge Liang's. Thus, he created a corpse of himself through the separation of Zhuge Liang's Spirit Core. This action left him without nearly all of Zhuge Liang's powers though. However, it also allowed him to investigate without being deteacted as a Servant. He then reveals the Singularity's vast mana increased the normally inefficient energy drawn from their memories. Using the scraps caused the Singularity's vast mana to encroach on their memories and fabricated them, which is the enemy's goal. El-Melloi II suspects Ritsuka's memories were stolen from the moment they arrived. However, even with their memories stolen though, fabricating memories would be prove difficult since their memories of a particular Servant would resurface if they reencountered them. Thus in the order to rewrite memories, the enemy arranged the scraps to placed at a certain locations for Ritsuka to retrieve. The first and second scraps contained Ritsuka's original memories, while the third was meant to implant fabricated memories. El-Melloi II concurs with Gray that Chaldea would know whether Ritsuka's memories are true or not. He questions though why they've been only received transmissions from Mash, and explains the enemy needed someone Ritsuka absolutely trusted to guide them. Reines then deduces the "M" in El-Melloi II's messange was for Mash. El-Melloi II reveals the Mash they've been talking with so far is fake. After "Mash" blocks communications, he explains the enemy fabricated her in order to get the group to believe in her information reports in order to guide them. He deduces the enemy's goal isn't to destroy them, but rather something to do with the scraps. He cannot deduce anymore though with his analysis of the final scrap, but he says Babbage could provide a deeper analysis. The group then return to Babbage's castle with El-Melloi II, Astraea, and Kerry.
Babbage agrees to analyze the scrap, believing it may provide clues to the enemy. He then invites the group to rest in his castle since the analysis will take time. He believes the enemy would know why Ritsuka needed false memories implanted into them when Astrae asks why. He also wonders what particular memories of theirs were being erased. El-Melloi II deduces the enemy pities them, with good yet ill intentions. Reines then realizes she, Luvia, and Gray were summoned because El-Melloi II failed. She explains he failed when he created the corpse because he was driven into a corner. She, Gray, and Luvia were more inclined to be summoned due to their deep connections with him. She then deduces they were summoned as Servants due to Zhuge Liang's Noble Phantasm, Chu Shi Biao. El-Melloi II explains it grants allies the abilities they need, and in this case, providing Reines, Gray, and Luvia with Servant Saint Graphs. Its effects wouldn't be that tremedous though unless the Singularity's circumstanced put a strain on humanity. Reines deduces Sima Yi was summoned thank to his connection with Zhuge Liang. Later, El-Melloi II reveals the Singularity was ready to collapse when Ritsuka woke up, so it consumed their memories to lengthen its lifetime. The group then rush to the castle's balcony when Reines retrieves them. Reines realizes their awareness of the Clock Tower was obstructed, so they never realized it was a fake Rhongomyniad. Babbage reports a large number of steam ghosts and automatons are emerging from its interior, though they seem peaceful for now. They seem peaceful for now, but Babbage warns there's an 80% of them invading to capture Rtisuka. He then gives his analysis of the final scrap, revealing the enemy is related to Chaldea. El-Melloi II assumes they're a traitor since they knew both Mash's appearance and mannerisms. Babbage then gives the second name revealed in his analysis: Mnemosyne, a system of Chaldea. Reines and Astraea decide to assault the fake Rhongomyniad, but Babbage warns against it with all of the enemies swarming out. Gray says she could clear a path, but she lacks sufficient mana to do so. El-Melloi II suggests collecting the smaller scraps for mana, and asks Babbage to provide a countermeasure against their fabricated memories.
Joined by Babbage, the group search for the smaller scraps, and fight through their fabricated memories. A memory of fighting Ultra Heroine Z, except a alternate version of Mysterious Heroine XX called Super Heroine ZZ also joins in. A memory of the first battle against Gawain at Holy City Camelot's main gate during the Camelot Singularity, but his Gift of Nightlessness doesn't function. A memory of the battle against Black Iri, though she later transform into a corrupt version of Illyasviel von Einzbern. A fabricated memory of fighting Medea and Heracles during the Okeanos Singularity. A fabricated memory of fighting a horde of corrupt Musashibou Benkeis, who are weakened by Ushiwakamaru's Benkei - Steadfast Position and finished off by Jumping the Eight Ships at Dan-no-ura. 
With the smaller scraps collected, Gray uses their mana to create a crystal stairway to the fake Rhongomyniad. While Ritsuka, Reines, Gray, and Astraea ascend the stairs, Babbage, El-Melloi II, and Kerry prepare for the onslaught of automatons and ghosts. Meanwhile, Bunyan, Jack, and Kintoki, the Queen, and Shakesperare defend their respective Patchworks from the automatons and ghosts. The group continue ascending the stairs when they're transpoted into a fabrication of the Battle of the Time Temple by a sudden Mnemosyne scrap. There they are confronted by fabrications of Lev Lainur Flauros and Barbatos. Ritsuka recalls fighting Barbatos in the London Singularity, and Reines realizes the enemy is using that link to create the fabrication. Astraea then proceeds to bombard Barbatos and the Demon Gods of the Control Room with Custos Morum. Reines uses her Noble Phantasm to extract Ritsuka's memories of fighting the Demon Gods as magic. After the group fights against Barbatos several times, Reines uses Unspeakable Formation to rewrite the fabrication into the true memory of when Ritsuka destroyed the Demon Gods. After destroying Barbatos, the group exit the fabricated memory, and continue ascending the stairs.
Eventually the group enter the fake Rhongomyniad's interior, but Astraea is suddenly forced outside. The enemy explains they created the fabricated memory from earlier in order to weaken Astraea since she was a major threat. Taking on the appearance of Da Vinci, the enemy reveals she was originally a formless program; Reines deduces she is Mnemosyne. Mnemosyne reveals she is a subsystem for verifying reality at the moment of rayshifting. Prior to rayshifting, Staff members would verify reality at the destination to ensure the Master's safety. Mnemosyne was created as a system to ensure the Master still existed in the case of the staff being dead. However due to technical issues, she was never implemented. Reines realizes Mnemosyne is trying to ensure Ritsuka is protected. Mnemosyne demands the group hand Ritsuka over, and proceeds to fight them. The battle ends when they're struck by something akin to a Noble Phantasm. Reines deduces Mnemosyne is using the memory of Rhongomyniad since the fake one is her body. She tells Gray to use Rhongomyniad, but Add says he isn't able to. Mnemosyne reveals she can interfere with Gray's Rhongomyniad to prevent its activation like Gray can also do. She did so before the group arrived since it would be their key to a swift victory. She then proceeds to use the Grail to transport Ritsuka into a space of memories.
In the space of memories, Ritsuka is shown Mnemosyne's oldest memory during her construction. However since she was never completed, she could only observe the Incineration of Humanity. After humanity was restored, her data was transferred into the Shadow Border, which changed her heavily. Mnemosyne reveals she reawakened when the Chaldean survivors established their base at the Wandering Sea. Upon awakening though, she disovered A-Team betrayed humanity, and the world turned blank by the Fantasy Trees. Upon discovering her creator, Da Vinci, was dead, Mnenosyne used her functions of observation in the conjunction with her Grail to create the Singularity. She also decided to use her power over memories to erase Ritsuka's painful memories after realizing she could use her observations to determine what's true. She reveals she created the three Mnemosyne scraps to take their memories in order to guide to them. This was done to create new memories, and to make it easier for Ritsuka to accept them. Mnemosyne however didn't want to simply give them to Ritsuka, but having them go through proper tribulations to turn Ritsuka into their utmost version of themselves. That intention though was ruined by El-Melloi II's intervention, for which she apologizes. She tells Ritsuka to receive her memories, and proceeds to erase their memories. However, Gray uses Rhongomyniad to create a link into the space. Mnemosyne claims the effort is too late though, as she already has complete control over Ritsuka and their memories. She argues with Reines that Chaldea has been too tragic for Ritsuka, claiming she awakened to save them from their flaws and sorrows. Ritsuka however refuses to let her take their memories away. Mnemosyne replies she will need to break them, believing they are lying to themselves to cope. She decides she will keep with her for many years until they are completely healed. However to her shock, something breaks through the exterior of the fake Rhongomyniad. It is revealed M used his Noble Phantasm at the cost of his life to increase its distance and damage output.
With Ritsuka out of Mnemosyne's space of memories, Astraea enters the fake Rhongomyniad's interior. She uses her second Noble Phantasm,Iam Redit et Virgo, to clear the sky of the smog that blocked Chaldea's communicators. Mash reveals they lost contact with Ritsuka after they rayshifted, but they still had their location. Reines then reveals the motives for each Patchwork. Patchwork Fairy Tale wanted to be searched for; Patchwork Masquerade wanted to talk without their identiies being known; Patchwork of Dazzling Steam wished to forget. Reines concludes Mnemosyne created the Singularity centered around memory loss because she was the one who wanted to saved. Trimmau reveals Mnemosyne and the fake Rhongomyniad is weakening due to Astraea's Noble Phantasm, so the group use this opportunity to finally defeat her. After being defeated, all of the memories that Mnemosyne collected begin to spill out from her. The fake Rhongomyniad then begin to collapse as well since it is her body. The group escape before it finally collapses.
With the fake Rhongomyniad now destroyed, everyone begins to disappear with the Singularity's imminent collapse. Astraea and Reines both wish the bonds they formed with Ritsuka will let them be summoned to Chaldea before disappearing. Meanwhile, Mnemosyne accepts she will lose the mana granted by the Grail and the Singularity will be resolved. She finally shuts down after Da Vinci praises her for her work.
At Chaldea, El-Melloi II apologizes for getting Ritsuka into such a dangerous situation. He also deduces the Da Vinci that appeared before Mnemosyne at the end was Reines using Unspeakable Formation on her. It is then revealed El-Melloi II had accidentally brought Gray back with him. Gray reveals she has the Grail Mnemosyne used, and Da Vinci deduces it responded to the real Rhongomyniad and Gray's wish to stay with El-Melloi II. Goldolf commends her for bringing back the Grail, calling it a physical record of her accomplishment. Ritsuka then welcomes her to Chaldea.
|Rider||Sima Yi||Ritsuka Fujimaru|
|Berserker||Paul Bunyan||Patchwork Fairy Tales|
|Berserker||Sakata Kintoki||Patchwork Fairy Tales|
|Assassin of Black||Jack the Ripper||Patchwork Fairy Tales|
|Caster||Nursery Rhyme||Patchwork Fairy Tales|
|Archer||James Moriarty||Patchwork Masquerade|
|Caster||William Shakespeare||Patchwork Masquerade|
|Saber||King Arthur (Alter)||Patchwork Masquerade|
|Caster||Charles Babbage||Patchwork of Dazzling Steam|
|Caster||Zhuge Liang||Ritsuka Fujimaru|
|Assassin (Fabrication)||Ultra Heroine Z||N/A|
|Foreigner (Fabrication)||Super Heroine ZZ||N/A|
|Avenger (Fabrication)||Irisviel von Einzbern (Blackened)||N/A|
|Avenger (Fabrication)||Illyasviel von Einzbern (Blackened)||N/A|
|N/A (Fabrication)||Musashibō Benkei (Blackened)||N/A|
|Mystic Code||Trimmau||Sima Yi|
|Magus (Fabrication)||Lev Lainur Flauros||N/A|
|Demon God (Fabrication)||Barbatos||N/A|
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Fate/Grand Order - Lady Reines Case Files, Act 11: Towards the Extremities of Records and Memories
- ↑ 2.0 2.1 2.2 2.3 2.4 Fate/Grand Order - Lady Reines Case Files, Act 2: Searching for a Neverland's Denizen
- ↑ 3.0 3.1 3.2 3.3 3.4 Fate/Grand Order - Lady Reines Case Files, Act 3: Masquerade
- ↑ 4.0 4.1 4.2 4.3 Fate/Grand Order - Lady Reines Case Files, Act 9: A Magus' Deduction
- ↑ 5.0 5.1 5.2 5.3 5.4 Fate/Grand Order - Lady Reines Case Files, Act 8: The Final Scrap
- ↑ 6.0 6.1 6.2 6.3 6.4 Fate/Grand Order - Lady Reines Case Files, Act 7: King's Memories
- ↑ 7.0 7.1 7.2 7.3 Fate/Grand Order - Lady Reines Case Files, Act 10: The Fake Holy Lance
- ↑ 8.0 8.1 8.2 Fate/Grand Order - Lady Reines Case Files, Act 4: Arbitration Invitation
- ↑ 9.0 9.1 9.2 9.3 Fate/Grand Order - Lady Reines Case Files, Act 1: Magus' Disciple
- ↑ Fate/Grand Order - Lady Reines Case Files, Act 5: A Melodic Response
- ↑ Fate/Grand Order - Lady Reines Case Files, Act 6: Dazzling Steam
- ↑ Fate/Grand Order - Lady Reines Case Files, Saber Wars ?!
- ↑ Fate/Grand Order - Lady Reines Case Files, Deplorable Wall
- ↑ Fate/Grand Order - Lady Reines Case Files, Bullets and Grail...
- ↑ Fate/Grand Order - Lady Reines Case Files, To Deceive or To Be Deceived?
- ↑ Fate/Grand Order - Lady Reines Case Files, Master and Servant
- ↑ Fate/Grand Order - Lady Reines Case Files, Epilogue