Born in New York, John is the third son of his father, a mage who hide his magical status from most of his family, and his mother, who worked for the police. At a very young age, John saw his mother being incinerated to death, while on duty, when it was shown on TV and his father, who was nearby, quickly turned off the television to shield his son from seeing the harrowing scene. While mostly perceived as a phlegmatic individual, John's father was a loving parent that continued to take care of his family as he told a young John about his mother's achievements in order to bring solace to his child's mind. John later joined Orlando Reeve's Clan Calatin which benefited his father, who was estranged from the Mage's Association, as he would receive the American government’s financial backing. After learning the existence of magecraft, John was horrified when learning how useful magecraft could be for crime.
John has short, spiky blonde hair, light blue eyes, and a young-looking face that would allow him to pass for a rookie officer. He wears the same police uniform as the other members of Clan Calatin. After losing his hand and having it replaced with Dumas’ prosthetic,
John thinks of himself as a policeman first and a magus second, stating that it is his job to save as many people as possible. He became a police officer simply out of a desire for revenge, rather out of any noble or heroic desire liked False Caster presumed he had. While he is greatly impressed by the artificial Noble Phantasms provided for Clan Calatin by his chief’s Servant, he expresses doubt that they have an actual chance of winning the Holy Grail War.
As far as ordinary citizens are concerned, John could be called the ideal police officer, having spent his whole life chasing the shadow of his mother. While initially left confused by the revelation of the existence of magecraft, he accepted its reality after he began performing it himself, with his confusion shifting to fear. He could understand why other magi conceal Mystery, but he could not understand their willingness to sacrifice others for this end. Since he was raised as an ordinary person, he feels anger at the nature of mage society, and has a mindset completely different from most magi, unable to fully comprehend the kind of vast schemes undertaken by magecraft organizations like the Mage’s Association and Holy Church. While he did not agree with Orlando’s willingness to cooperate with Faldeus Dioland due to Faldeus’ plan to sacrifice Snowfield in the situation that things go awry, he begrudgingly accepted that he could do nothing to oppose the government, and that attempting to save as many civilian lives as possible was the most reasonable course of action in these circumstances.
He is normally cautious and perceptive when in a dangerous situation, but ultimately self-sacrificing. When the Clan Calatin officers are confronted by True Archer with the moral dilemma of sacrificing his life to save that of a child, John opens his mouth without thinking, stating that the logical decision would be to flee and allow the child to die, but that he is afraid of abandoning the child in exchange for a future and a cool head.
When False Assassin attacks the police station, John and the other Clan Calatin members try to fight her off, doing rather well, but she kills several of them. Suddenly, her Master Jester Karture arrives and teleports her away with a Command Spell. Jester takes over the battle and kills several of them, and cuts off John's right hand when he tries to stab him. They are saved when Hansa Cervantes intervenes and battles Jester, eventually forcing him to retreat.
False Caster gives Clan Calatin new Noble Phantasms and gives John an artificial hand that has a built-in dagger coated in Hydra venom. False Caster takes a liking to John, recites his history, and says he has potential. The officers ask if they actually stand a chance in the war. False Caster says he is not sure, but they can make a difference.
Orlando assigns the officers to secure Tsubaki Kuruoka, a young comatose girl who is the Master of False Rider. When they arrive at the hospital, True Archer arrives, intending to kill Tsubaki. He summons the three-headed hellhound Cerberus with his Noble Phantasm, King's Order, to attack the officers and they find themselves outmatched. Around this time, False Caster decides to use his Noble Phantasm, Musketeers' Masquerade, on John to turn him into a true hero. False Berserker arrives and defeats Cerberus, but is defeated in turn by True Archer.
False Archer, Saber, False Assassin, and Sigma arrive, but False Archer becomes offended by Saber and attacks him. After observing their battle for a bit, True Archer turns to the officers and says he has no quarrel with them, so if they will stand aside and let him murder Tsubaki, he will spare their lives. John steps forward and says he will fight to the end to defend the child. True Archer says he is brave, and for that, he pities him. He strikes John with his bow, launching him into a building and breaking his neck. John expects himself to die, but mysteriously feels no pain and is not losing consciousness. He is then surprised when he sees a vision of a time when False Caster in his original life as Alexandre Dumas met Edmond Dantès.
John is healed and empowered by Musketeers' Masquerade. He rejoins the battle, to the shock of his fellow officers and True Archer, then knocks True Archer back with a flying knee. He attacks True Archer with punches and kicks, and his strength is now great enough to hurt him. He then draws his Hydra venom dagger, which horrifies True Archer and makes him jump back. John tells the other officers to secure Tsubaki while he keeps True Archer busy. True Archer draws his bow and declares John a worthy opponent.
While John continues to battle True Archer, his fellow officers try to assist him, only to be scattered by arrows. False Berserker reappears and attacks True Archer from behind in the form of a squad of officers, but True Archer slashes at them without even turning around, keeping his attention on John. False Berserker attacks again and manages to bind True Archer with hands from shadows.
True Archer spots False Berserker's Master Flat Escardos and seemingly kills him, but he turns out to be a duplicate while the real Flat was hidden in the squad and uses a spell combined with his second Command Spell to disrupt the Servant's flow of magical energy by targeting the From Hell he stole, nearly causing his body to fall apart. John then stabs him in the side with the dagger so hard the dagger breaks. As True Archer's body is slowly eaten away by the venom, he asks False Berserker why he risked his Master on the battlefield, so they explain how they needed that second Command Spell for their plan to work. True Archer congratulates all three of them for doing all this damage to him without divine aid, but then says it is not enough. To their horror, Black Mud erupts from his wound and absorbs the venom before flowing back inside him and healing the wound. A tornado of magical energy erupts from him, knocking them back. He suddenly decides they are beneath his notice and leaps away to attack False Archer instead. Later, a wave of blackness washes over the street. When it passes, John and all the other combatants have vanished, to the shock of those observing.
John sees another vision of the time Alexandre Dumas met Edmond Dantes. He wakes up next to his fellow officers, who confirm they saw the same thing. His artificial hand is damaged. They ask him how he became so powerful and he says he is not sure, but he thinks False Caster did something to him. They look around and are shocked because they seem to be in the same place they were before, but the streets are empty and undamaged as if there was no battle.
They explore the city and find a few people whose minds have been seized by something, and discover if they try to walk out of the city, they are warped back into it. They come to the church and find Ayaka Sajyou and her Saber. His fellow officer Vera Levitt does the talking to invite them to work together. They conclude they are in an isolated space, possibly a Reality Marble, and they must eliminate whoever is causing it to escape.
While he did not inherit his family's Magic Crest, John is capable with magecraft, and has decent skill with both hand-to hand-combat and weaponry. After losing his right hand to Jester Karture, False Caster gives him a prosthetic hand that has a built-in dagger coated in Hydra venom which can be deployed and retracted as John wishes. The venom is highly potent, being a poison from the Age of Gods that has killed countless heroes, and a danger in particular to True Archer. If not for the Grail Mud given to him by his Master, a single wound from the blade coated with the venom would have killed him.
After being healed and empowered by Musketeers' Masquerade, John's strength, speed, and agility increase dramatically, making him capable of moving at the speed of a bullet and matching True Archer in combat. His bare-handed attacks are not enough to actually harm True Archer with strength alone, and below the level of a martial Heroic Spirit, but the Servant is nonetheless impressed and compares his brute strength to that of the ancient Greek generals he fought in life. By putting all of his enhanced strength into an attack, John can strike a blow at supersonic speeds. While still insufficient to inflict any real harm on True Archer on its own, the shockwave produced by the strike sends Flat Escardos and the nearby rubble around the battle flying, and snaps the Hydra venom dagger off of John's prosthetic hand at the base.
- Fate/strange Fake Volume 4 - Chapter 12: Day 2, Daytime "Genius Was Not Built in a Day; All Magecraft Leads to Disaster"
- Fate/strange Fake Volume 5 - Chapter 14: "Gold and Lions I"
- Fate/strange Fake Volume 1 - Prologue IV: "Caster"
- Fate/strange Fake Volume 2 - Chapter 3: Day 1, Early Dawn "Ensemble Versus Illusion"
- Fate/strange Fake Volume 2 - Chapter 4: Day 1, Before Dawn "A Battle Without Heroic Spirits"
- Fate/strange Fake Volume 4 - Chapter 13: Day 2, Night "At Last, a Second, and a Third..."
- Fate/strange Fake Volume 5 - Chapter 15: "Gold and Lions II"
- Fate/strange Fake Volume 5 - Chapter 16: Day 3 "Breaking Dawn and Wakeless Dreams I"