"The Fifth True Ancestor? I've never heard of that—I've only heard of the Fourth," Himeragi Yukina said, shaking her head.
Any properly trained magus-enforcer knew the term "Fourth True Ancestor." Even without much contact with the outside world, she'd heard it.
"I don't mean her. I mean the impossible Fifth True Ancestor—the one who devoured her."
"W-what…?" Yukina wondered if she'd misheard.
The Fourth True Ancestor carried the epithet "the world's strongest vampire." She'd never claimed it herself, but that was the common belief.
And that being had been devoured?
"I thought the Fourth True Ancestor was just an urban legend. Does he—she—really exist?" Yukina asked, incredulous.
"She does, and she was indeed devoured by the Fifth," the woman replied.
"If that's true… then what is the Fifth True Ancestor?" Yukina couldn't very well doubt the Three Saints; the question slipped out in a whisper.
"I haven't met him myself, but someone has," the woman said, a teasing note in her voice.
"Huh?" Yukina wasn't sure if she was imagining it.
"Back to business," came another female voice from behind the curtain—plain, but distinctly youthful.
"Alright, alright," the first woman answered, amusement obvious.
"Himeragi Yukina, the existence of the Fourth True Ancestor threatens the world's order and stability. You understand why, don't you?"
"Yes," Yukina said, grave. She'd studied this.
Vampire-kind with the "blood-drinking" trait and the more educated, civilized vampires weren't single-mindedly hostile to humans; many preferred to blend into human society and have, to this day, carefully avoided all-out war with humanity.
And each nation has treaties with the True Ancestors prohibiting indiscriminate blood-drinking.
But that surface-level peace exists only because the three Night Empires are balanced in power.
The three True Ancestors agreed to the Sanctuary Treaty because, for decades, they've checked one another, maintaining a stalemate of three great powers.
They fear other True Ancestors besides themselves; they have no free hand to fight humanity.
That was the doctrine Yukina had learned.
By those lights, if a fourth True Ancestor of comparable strength appeared, the balance would collapse easily; in the worst case, it could spark a large-scale war that engulfs humanity.
Worse still, this rumored Fifth True Ancestor had devoured the "strongest vampire," the Fourth. How powerful must he be?
If he aided any one of the other three, the situation would spiral out of control—or the three might even join forces against him.
A True Ancestor's familiars can destroy the world; if all four went to war, the world might simply end.
Humanity cannot allow that.
"Have you determined where the Fifth True Ancestor is?" Yukina asked, her voice tight. A bad premonition gnawed at her.
"Mm. Confirmed beyond doubt," came the answer—again with that teasing edge.
"Where is he?" Now wasn't the time to worry about tone.
"In Tokyo Metropolis, Itogami City—the Demon Sanctuary on the artificial island."
"What? The Fifth True Ancestor is in Japan?"
"Correct. That is why we summoned you… Himeragi Yukina, by the authority of the Three Saints of the Lion King Organization, I order you to monitor the Fifth True Ancestor."
"Eh? You want me to monitor him?" Yukina froze.
"Not only that—if you judge the target to be a clear danger, you are to eliminate him."
"Eliminate…"
Yukina wavered. How was she supposed to kill the Fifth True Ancestor?
She understood her own capabilities—and those of a True Ancestor. A True Ancestor's combat power could match a national army; they were true monsters, with ageless bodies and overwhelming regeneration.
How was she supposed to eliminate that?
"Himeragi Yukina, don't worry. Take this."
The curtain parted slightly and a beautiful silver spear floated out.
"This is—?"
"The Mechanical Demon-Purging Assault Spear Mark Seven (Schneewalzer), codenamed Snowdrift Wolf. You know the name, don't you?"
Yukina nodded silently. The Mark Seven spear was a weapon the Lion King Organization had developed to counter demons with special abilities.
Its tip was forged by advanced metallurgical refinement; its sleek lines rivaled the latest fighter craft—the term "assault spear" was apt.
Because its core incorporated an ancient holy lance, it couldn't be mass-produced; only three existed in the world.
Even so, among weapons a single operative could wield, it was top-tier—one of the organization's secret treasures.
"You're… giving this to me?" she asked softly, accepting the spear.
"Yes. Since your opponent is a True Ancestor, we intend to equip you adequately. As things stand, this is the strongest divine armament we can provide. Will you accept it?"
"Yes, of course. But… what's this supposed to mean?"
Another item drifted out from the curtain—not a weapon this time, but a uniform sealed in plastic: a sailor-collared blouse and pleated skirt in white and blue—clearly a girls' school uniform.
"This is a uniform—in your size."
"Um… why are you giving me a uniform?"
"Simple. Your surveillance target is at the school that uses it."
"Huh? The Fifth True Ancestor is a student? He goes to school?"
"Wrong—he's a teacher. A teacher in the junior division at Saikai Academy. That's the Fifth True Ancestor's current identity—Shichen. Since we have no one else well-placed to approach him, we're sending you, Himeragi Yukina."
"Shichen… Wait—this man in the photo is the Fifth True Ancestor?!" Yukina finally put it together, eyes going wide as she looked down again.
"Correct. From now on, you are to get close to him and monitor his actions. Your transfer paperwork to Saikai Academy is already complete. Do your best."
"…"
Remembering those moments from a few days ago, Yukina couldn't help sighing.
Fifth True Ancestor. Transfer. Approach. Monitor. Eliminate… Just thinking about it made her stomach hurt. Was this really something she could do?
And why her? Wouldn't it be simpler to send someone who could be hired as a teacher?
"Yukina, why the sigh? Still worried?" Akatsuki Nagisa came up, concerned.
"I'm fine… just not used to things yet," Yukina said, glancing at Avrora and Kaguya following behind Nagisa.
Both were vessels of the Fourth True Ancestor, identical in face; one wore a bright, innocent smile, the other seemed lost in thought—neither looked the least bit scary.
"Transfers are like that—you'll be fine in a few days. Come on, I'll introduce you. This is Avrora, and this is Kaguya."
"Um, I'm Himeragi Yukina. Nice to meet you," Yukina said, taking the initiative.
"H-hello…" Avrora gave a small wave, a bit nervous—still shy with strangers.
"Hello," Kaguya nodded lightly—then went back to thinking about how to give herself to Shichen.
Her hair had grown out—down to her shoulders now, just to his taste.
She couldn't afford to wait; the other sisters were all watching for their chance. She wanted to be the first.
"Yukina, they're a little shy—don't mind it," Nagisa said.
"It's fine. I'm shy too," Yukina replied with a shake of her head.
"Great. Let's get to the gym."
"Yes, yes—let's go. I want to see Shichen already," Avrora said, excited.
"You really like Shichen-sensei, huh, Avrora."
"N-no I don't…" Avrora denied, flustered.
"Let's go," Kaguya said, leading the way out of the classroom.
Nagisa and the rest followed close behind.
They reached the gym quickly, and there—at the entrance—stood the person all four cared about most, waving them over.
Yukina looked at Shichen, and for some reason it felt like the whole world's focus centered on him.
So this was the impossible being above the other True Ancestors—the Fifth True Ancestor?