Fate/Britain Lostbelt : Hero of Justice

Although Fuyuki is merely an ordinary coastal city in Japan, the existence of rich and active ley lines has made it home to several ancient magus lineages.

Currently, three mage families are publicly known to reside in Fuyuki: the Tohsaka, Matou, and Sajyou families. Shirou's friend, Shinji, mockingly refers to them as the "Three Great Families of Fuyuki."

The Tohsaka family has been the traditional caretakers of Fuyuki's land-bound ley lines for generations. It's even said that one of their former heads had once been a disciple of a true Magician, giving the Tohsaka a position of prestige—rightfully making them the leading family of the three. That was true up until a decade ago, when the previous head of the Tohsaka family passed away, causing the household to rapidly fall into decline.

The current head of the Tohsaka family is a girl the same age as Shirou, named Tohsaka Rin. Compared to Shirou, Rin can be considered a prodigy. She possesses forty primary Magic Circuits and an additional thirty sub-circuits, giving her a total magical capacity of 500 units.

This information was told to Shirou by his underclassman, Matou Sakura. Sakura also warned him that Tohsaka Rin was an arrogant, sharp-tongued girl, as cunning as a fox. She cautioned Shirou to be especially careful around her, lest he fall into one of her unseen traps and get thoroughly devoured—metaphorically speaking.

Sakura always described Rin this way, as though Shirou would be completely bewitched the moment he met her—just like a scholar seduced by a fox spirit.

—— But Shirou doesn't see her that way. In his eyes, Tohsaka Rin is a nearly perfect noble lady: graceful in manner, composed in action. Without even realizing it himself, Shirou finds himself admiring… perhaps even falling for that flawless Rin.

Compared to the Tohsaka family, the Matou family has a shorter history in Fuyuki. They migrated there roughly two hundred years ago. However, due to incompatibility with the land and other factors, the Matou bloodline quickly lost its aptitude for magecraft. Even Matou Shinji, who is the same age as Shirou, was born without a single Magic Circuit.

If nothing unexpected had occurred, the Matou family would have eventually lost all ties to magecraft and faded into obscurity, becoming ordinary people.

That was until Matou Sakura, a successor rivaling Tohsaka Rin, came into the picture.

Capable of releasing up to one thousand units of magical energy in a single burst, Sakura inherited the position of family head. Her brother, disinterested in the backstabbing world of magi, happily relinquished the role, allowing the Matou family to begin its road to restoration.

Matou Sakura is one year younger than Shirou. The two first met during the great fire that ravaged Fuyuki ten years ago—a fateful encounter that bound them together with ties no force could ever sever. Since becoming the Matou head, Sakura visits Shirou's home every day, spending time with him like family.

Even so, Sakura rarely speaks to Shirou about the world of magi. She doesn't want him to be tainted by the cruelty, selfishness, and cold logic that define magi. Shirou, in turn, refrains from practicing magecraft in her presence—perhaps part of why it took him so long to correct the flawed teachings passed down from Kiritsugu Emiya.

Compared to the Tohsaka and Matou families, the Sajyou family, which moved from Tokyo to Fuyuki in 1991—thirteen years ago—remains shrouded in mystery.

Shirou only knew one thing about the head of the Sajyou family—his name: Sajyou Hiroki. It was said that their magecraft bordered on black witchcraft, closer to that of witches than magus. Sajyou Hiroki was rumored to have two daughters who had never once appeared in public. Beyond that, information about the family was nonexistent.

Ever since the Sajyou family moved into Fuyuki, they had never made a public appearance. They seemed to fully embody the magus's creed of secrecy, adhering strictly to the principle of avoiding public attention. The only exception was an incident that happened ten years ago.

Taking advantage of the sudden and mysterious death of the previous Tohsaka family head, Sajyou Hiroki purchased the leyline property rights that had formerly belonged to the Tohsaka family—at an outrageously low price. He left them only nominal management rights. Through what could only be called opportunistic exploitation, the Sajyou family had effectively supplanted the Tohsaka as the true head among the Three Great Families of Fuyuki.

When Matou Shinji mentioned this to Shirou later, he couldn't hide the grin on his face. He stood in the student council room, laughing with vulgar satisfaction:

"Watching that Tohsaka girl stomp her feet in frustration was the best thing I've seen in ages! Hahahaha! Let that stuck-up princess rot in poverty and spend her life working for others. Heck, if she ends up so broke that she has to work as a maid, Shirou, I'll drag you along to visit—so we can both laugh our asses off! Hahahaha!"

Shinji's misogyny and deep-seated resentment toward women seemed to manifest most intensely toward Tohsaka Rin—despite the fact that he had never actually spoken with her directly. Shirou could only interpret this as a symptom of the inherited animosity between magus families—perhaps a consequence of the strained magical dynamics between the Tohsaka and Matou bloodlines.

Fortunately, it never escalated into open conflict.

The Sajyou family remained shrouded in mystery. As far as Shirou was concerned, his interaction with them was effectively zero. He had never once seen Sajyou Hiroki, nor had he ever glimpsed the elusive daughters he was said to have… or had he?

A sudden pain stabbed through Shirou's mind.

For some reason, his memories drifted back to five years ago—when Kiritsugu Emiya passed away.

At the time, Shirou had fallen into a deep depression following the loss of his adoptive father. Emotionally disoriented, he made an impulsive decision to do something utterly foolish—something he would never have done under normal circumstances.

He ran through the schoolyard at dusk, again and again, leaping over the high-jump bar.

It was a pathetic act. Shirou couldn't possibly clear that height, and yet, as if punishing himself, he kept trying. Over and over.

That evening, Matou Sakura silently watched him from a distance. But she didn't stop him. Beneath the twilight sky, it was just a boy and a girl.

That's how he remembered it.

Except…

"Why are you trying to clear that height, Lord Shirou?"

In that moment, a voice—soft, unfamiliar yet somehow familiar—surfaced in his memory.

The vision grew hazy. Shirou couldn't recall the girl's face. But he remembered her features: blonde hair, a small, delicate figure, and a dress of emerald green.

He couldn't remember her face.

Only that she radiated elegance, like a dancing princess, and that her presence pierced directly into his heart.

"Is it because of your family's passing?"

"I understand. If Ayaka disappeared, I think I would be sad too."

"But even so—"

The golden-haired girl smiled. It was a dazzling smile, like a flower in full bloom—breathtakingly beautiful.

"Please, don't be sad anymore."

"I will grant your wish."

"I will bring you everlasting happiness."

"There is nothing I can't do. Nothing I won't dare to do."

"——Even if it means becoming an enemy of Human Order."

With the gentleness of a whispered vow, the delicate girl embraced Shirou.