Hiroki Sajyou is a magus from a prominent foreign magus bloodline. He seeks the Root just like any other magus.
At some point in the past, he marries his wife (who is from an English background), who then gives birth to his daughters Manaka and Ayaka. His wife soon dies some time after creating her botanical garden, "Garden", due to both having a weak constitution and additional leftover strain from Ayaka's birth.
Hiroki Sajyou is a strict man who maintains a strict bearing towards his daughters on the surface. But, in truth, Hiroki deeply loves both his wife and his daughters and later shows regrets that he couldn't raise them better. Additionally, despite initially appearing to favor Manaka more, he insists in one of his journal entries that he loves both of his daughters equally and could never choose one over the other.
Prior to his wife's death, Hiroki was also a much more emotional and affectionate man, but after his wife's death, he returned to the mindset of a magus in order to deal with his grief. Hiroki later admits though that he regrets the decision, because it left his daughters with feelings of loneliness and minimized his function as a parent.
During the war, he displays weird behavior as a possible result of either Manaka manipulating him or of his growing awareness to Manaka's dark side, and becomes deeply disturbed and wary to the changes occurring in his daughter, Manaka. Despite this, he still tries to save both of his daughters, even though he ends up dying as a result.
Hiroki has dark brown and brown eyes. He is of fairly average height for an adult male.
Fate/Prototype: Fragments of Sky Silver Edit
In Fate/Prototype: Fragments of Sky Silver, Hiroki acts as a helper to his daughter Manaka throughout most of the First Holy Grail War.
At one point during the war, he takes Ayaka into Garden and explains to Ayaka that her mother had created Garden especially for her. He then tells Ayaka that Garden is hers from now on, and that she is to come here if something bad happens.
Day Two - Morning Breakfast With The Family Edit
On the second day of the Holy Grail War, Hiroki spends the morning with his family. After retrieving Ayaka, Hiroki comes into the dining room and sits down at the table with his coffee. While Manaka gets Ayaka to set the table as she cooks breakfast. Ayaka amazes at the amount of food Manaka is making and stares at her as she puts down the plate.
Noticing Ayaka's expression, Manaka teasingly asks "What's wrong?" to which Ayaka replies, "Nothing." Continuing her cooking, Manaka starts talking about how the English like codfish, while allowing Ayaka to sample the dish. Ayaka eats it and replies that "it's delicious," which makes Manaka happy enough to exclaims that she used a secret charm with the sour cream. Ayaka asks about the secret charm and Manaka replies that the one she used is more amazing than magic, making her father accidentally choke on his coffee at the same time.
Hearing that, Ayaka replies that their father told her that there was one thing more amazing than magic and Manaka replies saying that's why she used it. Manaka then gleefully exclaims that it's the "Magic of Love" and whispers into Ayaka's ear, that it's more amazing than any type of mystery that a Magus uses.
Day Three - First Battle with LancerEdit
On the third day of the Holy Grail War, Hiroki gets into a fight with Manaka about using Saber to lure out the other servants. Hiroki reminds Manaka that Servants are nothing more than weapons for the sake of the war, lumps of mysteries and argues that she should spend the day locked up at home. Manaka refuses, but Hiroki continues asking Manaka about what she is thinking and asks if she is capable of beating a Servant. Manaka says that she is and that she'll do something by herself, but Hiroki reminds her that the Holy Grail War is different from a magus vs magus battle. Jumping into the conversation, Saber remarks to Manaka that he agrees with her father and that he was summoned to fight with her. As Hiroki continues his arguments, Manaka comes up with the idea to do patrols instead.
Day Five - Training RegimentEdit
On the fifth day of the Holy Grail War, Hiroki watches as Saber spends the day doing intense training by fighting against dolls prepared by him. After the training session is over, Hiroki comments on the difference between Servants and magic tools and remarks that his dolls are useless in preparing Saber for Servant on Servant battles. Sensing that Hiroki is about to leave, Saber asks to accompany him and Hiroki replies that he doesn't mind. Saber thanks him. As they are about to leave, Hiroki sighs and relays his concerns to Saber about Manaka's reckless behaviour and how he feels that she may lose her life if she keeps this up. Seeing the concerned look on his face, Saber consoles Hiroki by agreeing that Servants are dangerous existences, no matter how excellent a Magus, Manaka is. In response, Hiroki asks Saber to take of his health and to entrust "that" to him. Saber agrees.
Day Nine - Conversation with SaberEdit
On the ninth day of the Holy Grail War, Hiroki meets with Saber and reports to him about Berserker's defeat and Rider's declaration of war. Understanding, Hiroki asks where Manaka is and Saber reports that she is in kitchen. Hiroki teases that Manaka is making something for Saber, but Saber remarks that she is also making something for him. Hiroki calmly remarks that Saber is a horrible liar and remarks that Manaka acts more human-like whenever she is with Saber. Surprised, Saber asks Hiroki about what Manaka was like before he was summoned. Hiroki replies that Manaka was a lot more empty and emotionless than she is now and had the ability to see through everything even her own future. Hiroki continues that this flourishing presence disappeared one day and Manaka lost all of her emotions as result.
He continues that around when their mother died, the wet nurse that Hiroki had hired had mentioned that Manaka was like a living ghost. Curious, Saber asks Hiroki feels about it. Hiroki sadly agrees that while Manaka makes light conversation with Ayaka, she does not really recognize Ayaka's existence. Saber comments that is too cruel and Hiroki agrees, but remarks that it is true. Slumping into his chair, Hiroki reiterates that Manaka shows more emotion now, but does not know whether that is a good thing or a bad thing.
After Rider's defeat, Hiroki becomes aware of the changes occurring in Manaka and becomes wary of her manipulative actions as a result. He then spends much of the second half trying to figure out what Manaka is up to and trying to figure out the whereabouts of the Greater Grail. He also additionally pulls Ayaka out of school for a while and confines her at home in order to protect her.
Day Fifteen - Preparing to confront ManakaEdit
That night, Hiroki meets with a doubtful Saber at the entrance of Garden. Confused, Hiroki asks Saber why Manaka isn't with him and asks why he hasn't received any reports from Caster about the search for Greater Grail's location since last night. Saber replies that he hasn't heard anything and silently wonders to himself if Manaka is keeping it a secret from her father too. Hiroki finishes Saber's thought and agrees that Manaka has been keeping secrets from both of them. Hiroki then looks over at Garden and informs Saber that Ayaka is there and he will bring her over to him. Saber tries to reject Hiroki's offer, but Hiroki insists while lamenting that he wasn't a better father to both of his daughters.
Looking down, Hiroki wonders who will protect Ayaka if a second Holy Grail War occurs and laments over his inability to protect his daughters if that were to occur. Turning away, Hiroki remarks that it is remarkable that Misaya survived the Holy Grail War and hints that he would feel more relieved if Saber would be the one to protect Ayaka. Hiroki then leaves while Saber is dazed from recalling his own failed relationship with his son, Mordred.
Day Sixteen - The Final BattleEdit
On the last day of the Holy Grail War, Hiroki places protection wards around Ayaka's room and heads out with Saber to find the location of the Greater Grail. In the car, Saber asks what Hiroki is writing and Hiroki explains that its a notebook with notes he has gathered on the Holy Grail War. Changing the subject, Hiroki continues explaining that as family head, he must interrogate Manaka because he cannot leave the issue with her alone. Saber apologizes, but Hiroki reassures Saber that he is not at fault as he is a Servant and not the Sajou's attendant. Hiroki then starts running down possible places where the Greater Grail could be.
Arriving at a church, Saber and Hiroki investigate the area. Sensing someone watching them, Saber calls out to the shadow and a man appears asking if they are both looking for the Greater Grail. After receiving the details from the man, Saber and Hiroki drive to the Greater's Grail location. During the drive, Hiroki senses that the magical barriers that he had placed to protect Ayaka have been broken by Manaka and wonders how she could that. As Hiroki further wonders why Manaka is in Ayaka's room, Saber becomes concerned and starts accelerating. When Hiroki asks why, Saber insists on heading to the Greater Grail as he senses that something is off. Hiroki agrees and they set off.
Arriving at the site of the Greater Grail, Saber and Hiroki meet with Sancraid Phahn who greets them. Asking why the Holy Church is protecting the entrance to the Holy Grail, Hiroki is instead attacked by Sancraid who sets off bombs which Saber blocks with his wind barrier. Avoiding the collapsing rocks, Hiroki insists that Saber goes on ahead, while he deals with Sancraid. After a brief fight, Hiroki manages to beat Sancraid by pulling out a gun and shooting him dead. Hiroki then continues onto the Greater Grail.
At the site of the Greater Grail, Hiroki confronts Manaka and tries to stop her by telling her to stop using the Grail for her own selfish desires. Manaka rebukes his attempts and eventually he is forced to use force in order to stop her. This fails, however, when the Beast grabs Hiroki and smashes him against the cliffs. Hiroki later dies from his injuries in the hospital, right after telling Ayaka that she will have to participate in the next Holy Grail War.
Hiroki Sajyou utilizes an old style of black magic that requires the use of animal sacrifices.