Kanata is from a declining magus family in a world where Tokyo was destroyed by a severe explosion during World War II that gouge the land to the point that it became a gulf. His paternal grandmother possessed Magecraft but kept to herself and eventually died when he was six. His father did not have Magic Circuits, so Kanata was raised as a regular boy, is untrained in magecraft, and does not know much about it. His father warned him not to practice magecraft in public and that magecraft does not lead to happiness. Despite the warning, he later demonstrated his slowdown magecraft at least once during elementary school to his friends such as Taka which was dismissed as just a trick.
His parents got divorced when he was in middle school putting him and his sister under their mother's custody and going by her family name. His father visits bi-yearly occasionally. He is in high school in the year 2020 (2nd year of the Reiwa Era).
By the way, he has a younger sister who apparently had potential and talent, so she separated herself from their family and became a freelancing magus.
He has a typical appearance of a 21st century Reiwa era Japanese male 17 year old. He has short black hair and possesses a vertical scar in the middle of his forehead. When he got sent to the past he was wearing a light colored shirt with a hoodie on top while wearing a dark backpack, he also had a dark colored pants with bright colored laced sneakers.
When he summoned Saber, command seals appeared on the back of his right hand in a shape that resembles an hourglass.
Kanata is not really interested in learning about magecraft and prefers to live a normal life. Having lived a normal life, he is unused to violence and death and quickly panics or freezes up when he sees people get killed. However, he does not hesitate to save his grandmother from Assassin instead of abandoning her and running away from certain danger.
Kanata was given a light novel by his friend Taka that claims an explosion that devastated the center of the then Imperial Capital of Tokyo and killed over 200,000 citizens 75 years ago was caused by a series of battles between supernatural beings. He fell asleep while reading it and dismisses it as just a story.
One day, his father visits and asks him to help liquidate his late grandmother’s estate by detecting any Mystic Codes she may have. While examining her things such as an old photo of her, he finds a strange hourglass and uses his power of slowing down objects on it when he drops it. To his shock, the hourglass reacts to his mana and time starts moving backwards. Unable to stop it, he sees events from the day repeat themselves before the time reversal accelerates. One of the flashes of the past he sees is of a younger him talking with his grandmother. He perceives himself falling and after seeing an explosion over Tokyo, blacks out.
He wakes up on a train after hearing screams. He sees a girl facing a Mysterious Officer and his Lancer. She orders him to evacuate to the rear car with the other passengers but to stay for questioning. While he can barely understand what is going on, the officer orders his Lancer to kill both of them. The girl grabs his hand and they run, explaining that he just appeared out of nowhere while she was being attacked by that Servant and Master. She is frustrated, though, by his lack of understanding what a Heroic Spirit is, despite him being a magus, and briefly explains the concept. She stops and decides to summon a Servant of her own, a Saber, to counter the Lancer and tells Kanata to keep a lookout. Just as she finishes the chant, the Lancer catches up to them and Kanata has to tackle her out of the way of his spear.
Lancer’s spear breaks Kanata’s backpack open and his light novel falls into the magic circle. The light novel acts as a catalyst, and Saber is summoned. It infuriated the girl when the Command Spells appear on Kanata’s hand instead of hers. Saber quickly kills the Lancer, which both terrifies Kanata and shocks him when he realizes she looks exactly like a character from the light novel. Saber asks him if he is her Master. Still confused, he says he is. She says their contract is established, holds his hands, and gives him a smile, stunning him with how beautiful it is.
The girl starts complaining about Kanata stealing the Servant she summoned and demands to know who he is. Suddenly, Archer appears; Kanata recognizes her from the light novel as well. Saber tells the two to run while she fights Archer. As they run, Kanata introduces himself and asks where is he and what year is it. The girl thinks he hit his head, but explains they are in the Imperial Capital in the 20th year of the Showa Era. Kanata realizes he is 75 years in the past and that the light novel depicted real events.
The Mysterious Officer tries to attack Archer from behind, but Archer kills him with a shot to the head. Kanata is again horrified by the casual murder, causing Archer to call him a coward. With him frozen in her as Archer tries to shoot him, the girl has to pull him out of the line of fire and drag him away. Kanata starts freaking out and complaining about his bizarre situation. The girl slaps him and tells him he needs to man up and fight if he wants to survive the Holy Grail War. He doesn’t know what that is, causing her to complain and briefly explain the concept.
Saber and Archer’s battle ends up destroying a large portion of the train, and Saber gets thrown into the car Kanata and the girl are in. He asks if she is okay, but she tells him to stay back and not risk himself being attacked by Archer. After Saber confirms with her that she has an ace up her sleeve, the girl asks her to use them right away and take down Archer before the train is completely destroyed. Saber retorts that she does not take orders from her, only from Kanata, her Master. Kanata is still confused and scared, but reluctantly orders her to do whatever it takes to defeat Archer. Archer catches up to them and tries to shoot Saber, but Saber uses Lightless, Three-Stage Thrust to dodge the bullets and stab her.
When Archer is forced to retreat, Saber grabs and examines Kanata’s face because his cheek is swollen from the girl slapping him. He thinks to himself his situation is unbelievable, but he has to accept he is in the past and experiencing events from the light novel. Saber says they should leave before people come. The girl introduces herself as Tsukumo Fujimiya and says she was supposed to be Saber’s Master. She then asks Kanata where he came from and what his goal is. Kanata finds she looks familiar, and upon hearing her name, he grabs her shoulders and stares at her face, shocking her and making her blush. He had seen her photo in his grandmother’s things and recalls a conversation he had with her where she asked what he wanted to be when he grew up, then said she had a dream of a bright future. He realizes Tsukumo is the past version of his grandmother.
He starts to cry because he thought he would never see his grandmother again after she had died in his time, alarming Saber and freaking out Tsukumo, but he brushes off their concerns. He tells Tsukumo he doesn’t know how he got there, telling himself he’ll keep their relation a secret to prevent a time paradox. As the trio salvages the train’s wreckage, he finds the light novel, but it’s damaged and its second half is missing. He reflects on how the book somewhat matched the events he just experienced, but seeing the Mysterious Officer’s corpse tells him this isn’t a story and that he can get himself killed. Saber apologizes for not adequately protecting him from Archer and promises to win the Holy Grail for him, then tries to persuade him to leave Tsukumo behind. Offended, Tsukumo says they’ll need her help to win. An air-raid siren sounds. When Saber doesn’t understand it, Tsukumo explains what it means and that their country is in the middle of a war, calling it a cruel joke.
Kanata and Tsukumo go around the Imperial Capital fascinating the former as he records it with his smartphone. He finds a newspaper that confirms he is in the past. They stop at a hotel and Tsukumo uses drawings to explain the seven Servants, Command Spells, and the Holy Grail. Kanata can’t believe something like the Grail exists but decides he has to win and use his wish to return to the future. Angered, Tsukumo slams his head into the table and pulls out a crystal that she claims can evaporate any liquid when activated. Calling his wish ridiculous, she threatens to explode his brain and kill him unless he agrees to fight for her wish.
Saber materializes and threatens Tsukumo with her sword. Kanata tells her to stand down and says he agrees to fight for Tsukumo, but Saber insists she only fights for Kanata. He and Tsukumo then surprise Saber by recognizing her as a member of the Shinsengumi from her uniform, as Saber did not believe they would become famous. Tsukumo gives them some money and orders them to buy some regular clothes to blend in. Outside, he checks his smartphone and, as expected, gets no service. He muses that he couldn’t find the hourglass that brought him here, and even if he somehow convinced Tsukumo of his true identity, there is no guarantee she could make it now. So his only hope of getting home is to win the Grail.
Saber buys a kimono. Kanata says it looks great, then takes her to a restaurant. Saber says she dislikes Tsukumo, but Kanata asks her to get along, as Tsukumo is important to him. Saber asks how that can be as they just met. He dodges the question by ordering ice cream. As commercial western ice cream hadn’t been introduced to Japan yet in her time, Saber is delighted when she tries it and amazed when Kanata says he eats it quite often. She then tries coffee but dislikes its bitterness. Kanata finds it hard to believe the vicious killer he saw last night and the cute, normal girl he sees now could be the same and asks Saber if killing bothers her.
Suddenly, soldiers from the Imperial Japanese Army walk up and point guns at Kanata. Saber kills them all in a split second, splattering Kanata with blood and traumatizing him. She says killing doesn’t bother her because she dealt with it all the time and that people who are bothered by death are the first to die. She wipes his face with a napkin and says he has to become stronger and get used to death, because he’s going to see a lot worse.
Kanata starts to freak out and vomits, saying he cannot get used to this and cannot fight. She says it is the Servant’s job to fight. Kanata asks why she would willingly serve a loser like him, then asks what her wish is. Suddenly his hand starts to vanish due to Assassin mortally injuring Tsukumo. He checks on the first half of the novel and notices the words are getting blurry and the story has been changed. He becomes horrified upon reading that his grandmother was killed in her teens and realizes the timeline has already started to change because of him, as getting ambushed by the Japanese Army wasn’t part of the story. Realizing that Tsukumo is in danger, he tells Saber that they need to go back to the hotel instead of hiding like she suggested and begs her to help him save Tsukumo. He remembers in the original storyline, his grandmother, who was supposed to be Saber’s Master, fought against the ghost of Tosa in an alley. He tells himself that he will never get used to bloodshed, but he will fight to save his grandmother.
Saber carries Kanata while jumping across buildings quickly heading back to the hotel before the future comes true. He contemplates how cold-hearted she is. His condition worsens as he begins to become weaker and his left hand is nearly gone. He and Saber then arrive at the hotel before Assassin could finish Tsukumo off. Furious and shocked at the sight of Tsukumo’s injuries, Kanata asks Assassin what he’s been doing to her. He later recognizes him as the ghost of Tosa and is horrified when Assassin demands he use his Command Spells to make Saber kill herself. He is hesitant to do so to save his grandmother’s life until Tsukumo convinces him to abandon her and escape. After Assassin pierces Tsukumo’s right hand through her shoulder, most of Kanata’s left face, entire arm and leg disappear. He collapses to the ground and struggles to sit up.
As he starts to disappear, Kanata tries to stay focus and think of a way to save his grandmother, but his memories of her and his childhood are fading out of existence. Before his memories and existence are completely erased, he hears Saber calling to him, and his body is restored somehow. He recalls about Saber in the light novel after he had a chat with his friend and he remembers one of the lines he read said “I can believe in you”. Coming up with a plan to save Tsukumo, he asks Assassin how Commands Spells work before throwing his smartphone and making it with his magecraft as a distraction. It buys him enough time to remember what his grandmother did first when she faced Assassin in the original timeline. He then uses his first Command Spell to order Saber to kill Assassin, which boosts her strength and speed. As Saber and Assassin battle, Kanata rushes to Tsukumo’s side to protect her. He holds her in his arm, as she is still unconscious. He warns Saber that Assassin is the ghost of Tosa and he can imitate any sword technique he sees.
He blames himself that Tsukumo got injured because of him until Tsukumo regains consciousness and he apologizes to her. However, she isn’t mad at him for not saving her sooner, but for using a Command Spell and asks him why he didn’t abandon her. Kanata still can’t tell her the truth and all he can do is comfort her. He later performs surgery on Tsukumo to re-attach her fingers under her directions.
After he is finished, Tsukumo compliments his good work and asks if he had prior experience in doing it before. Kanata gives her a vague answer while thinking to himself that he was glad he read Black Jack. Saber then returns, reporting that the corpses have been disposed of. Kanata notices her wounds are gone, to which Saber explains that Servants recover in spirit form. She regrets, though, that the clothes he got her got ruined and also that Assassin got away. Kanata tells that it doesn’t matter as long as she is fine, but Saber looks away in shame. Tskukumo advises that Saber return to spirit form to save on magical energy and to be a lookout. They all then leave the hotel when it gets dark.
While hiding from their enemies in the rain with Tsukumo, Kanata uses his smartphone to check the words on the pages changed back or not, but they’re still faded. The following day, he dreams of his grandmother in 1943 being the sole survivor of the Japanese Army’s attack. After Tsukumo finishes her call with the priest, Kanata informs her about the two soldiers from the Imperial Japanese Army, so they make their escape without being noticed. Kanata asks Tsukumo if her relatives could help her hide somewhere, but she reveals her family is dead and her father went missing two years ago. Suddenly she collapses from exhaustion and develops a fever from being in the rain and lack of sleep. Kanata carries her, determined to keep her alive in this era.
Kanata eventually locates an abandoned clinic for them to hide in. As Tsukumo regains consciousness, he informs her of the situation and gives her some medicine. Tsukumo tells him about another way to transfer his Command Spells to her without killing him. Kanata is hesitant though since his grandmother’s injuries still haven’t fully healed. After Tsukumo tells him her wish, he notices his grandma’s wish wasn’t written in the novel, but he doesn’t know how to feel about it. He then convinces Tsukumo that he will carry her despite his fears, and that he won’t run away. For that, he wants them to work together to put an end to the Grail War. He and Tsukumo then shake hands in agreement and he calls her by her first name. Afterward, Kanata tries to contact Saber through telepathy. He gets no response, and he thinks it’s fatigue given the fact he hasn’t eaten and/or slept for a few days. Tsukumo develops a fever again, so Kanata cares for her while she is sleeping. He notices he’s not fading away like before and thinks it’s a good sign that his grandmother is alive for now. He can also read some of the words in the light novel, though it’s still mostly blurry, and wonders if his grandmother was the author. He recalls his past with his father about how Kanata’s grandmother used to take him by the river when he was a child. Kanata’s father once told him the reason why his grandmother come the same place was because she was waiting for someone. Back to reality, Kanata reasons Tsukumo created the hourglass to stop the war and decides to finish what his grandmother started.
He later comes to Saber’s side to stop her and Oryou from killing each other. He explains to Saber that he wasn’t able to contact her telepathically, so he followed her path of magical energy. In his inner thoughts, he mistakes Oryou as Rider and the man in white as her Master, not knowing he is Rider. Saber, however, informs Kanata that the man is a Servant, but she has no idea who Oryou is. Rider and Oryou both claim that the two of them together are Rider. After listening to Rider’s request for cooperation to help take down Archer, Kanata asks what would happen if he refuses his offer. Rider explains they will leave them alone, but adds that the army has likely sent their way. He doubts he could escape in his current condition. Saber requests Kanata to use a Command Spell, so she may kill as many soldiers as possible. Kanata declines Saber’s request and is wiling to accept Rider’s offer under the condition he promises to save Tsukumo’s life. Rider accepts Kanata’s request and asks for his name. Kanata tells him his name and Rider thanks him for rejecting the path of conflict.
Later, at Rider’s hideout, Kanata hears Tsukumo screaming and finds she has already regained consciousness. He informs her of the alliance he made with Rider under the condition he treats her injuries. He also tells her that Saber is outside, serving as a lookout. Oryou fully restoring Tsukumo’s fingers with her healing ability shocks him, but he closes his eyes in embarrassment when she starts to heal the rest of her body. He asks if she’s okay, to which Tsukumo replies that she can’t marry anymore. Kanata reassures her not to worry and says she has to get married. Tsukumo responds that she was only joking and tells Kanata not to take it seriously. Kanata then sincerely thanks Oryou for healing Tsukumo, but she rudely rejects him since she still hasn’t forgiven Saber for turning her sword on them.
Before Kanata checks on Saber, Rider gives him some corn to share with her and reassures him that he and Oryou will keep Tsukumo company in the meantime. In his inner thoughts, Kanata notices how gentle Rider is and there are Servants like him. Afterward, he comes to the rooftop and asks Saber if she’s hungry, even though it isn’t necessary for Servants to eat. Regardless, Saber eats some corn with him. After telling Saber that he’ll buy her new clothes tomorrow, Kanata asks her if he really let her down. Saber says it’s her fault for letting the enemy show pity on them and how she got nothing, but shows how pathetic she is. Kanata denies it and asks her if this is how he feels about her. He tells her that if it wasn’t for her, both of him and Tsukumo would be dead. As long as they can still think about what to do in the future, it’s not over for them. Kanata’s words cheer Saber up a little as she expresses relief that he and Tsukumo are safe since she is important to him. Kanata then tells her the truth that he never had amnesia and he was sent back from 75 years in the future by a Mystic Code he found in his grandma’s house. He also reveals to Saber that Tsukumo is his grandma, who was originally meant to be her Master. He then shows her the damaged half of the novel, in which hers and Tsukumo’s exploits in the Grail War are written, and reveals the future will change greatly and he will cease to exist if Tsukumo dies. However, he only shows halfway through the book, but he knows the war will end with the capital being destroyed and becoming part of the sea. He thinks his grandma wanted to change the future.
The only magecraft Kanata knows is how to slow things that he has touched with his hands, such as slowing a falling glass of water so he can pick it up before it breaks and spills. It comes in handy when he uses it as a distraction after he throws his smartphone at Assassin to buy him time to save Tsukumo.
He is also good at stitching body parts after he successful stitch back Tsukumo's fingers due to reading Black Jack in the past.
 Fate/type Redline - Volume 2 - Glossary: Akagi Kanata [Master], p.202
Akagi Kanata [Master]
Saber’s Master. 17 years old. The oldest son of a family that quit the ways of magecraft in his father’s generation. He currently goes by his mother’s last name. As a magus, he’s a mediocre one who can merely decrease the speed of any object he touches. As for his personality, he’s just like any other modern human in that he’s become much too accustomed to peace. Having nothing to call a conviction of his own, he was thrown into the Holy Grail War through a crazy series of coincidences. By the way, he has a younger sister who apparently had potential and talent, so she separated herself from their family and became a freelancing magus.