The personalities of Yukino Yukinoshita and Haruno Yukinoshita are quite different.
The younger sister is serious, stern, rarely smiles, and speaks with brutal honesty.
The older sister, however, wears a fake smile no matter what she says and loves to act like a riddle-maker.
Even if there doesn’t seem to be any malice behind it, riddle-makers are sometimes truly infuriating.
Riddle-makers, get out of Chiba!
Get out!
“Why won’t you accept your big sister’s gift? It’s not anything valuable.”
“Setting aside the ‘big sister’ title for a moment—you just called this a priceless treasure, and now you’re saying it’s nothing valuable. Don’t you think your phrasing is a bit inconsistent?”
“Things always have diversity, Hikitani-kun.” (It’s Hikigaya.) “This mask contains a unique sealing technique created by yours truly—a genius sealing technique master—so in that sense, it is indeed a priceless treasure. But the materials were just things I found lying around the shrine. They cost no money to make, so it’s worthless to me. That’s reasonable, isn’t it?”
“Calling yourself a genius master… so this mask is what you used to seal me.”
Haruno Yukinoshita placed the mask back into Hachiman Hikigaya’s hand.
This time, Hikigaya didn’t resist.
Instead, he examined the mask carefully, turning it over and over.
The ice-blue patterns shimmered with a mysterious luster.
He could feel traces of power flowing within—faint but unmistakable.
Hikigaya had seen this kind of energy before.
The power that surged wildly when Himeragi used Sekkarou was exactly the same.
This woman also called herself a miko and used the same—or similar—cursed power as Himeragi.
But there was a key difference.
When Yukina Himeragi used cursed power, it was like using a sword: swift and sharp.
But when Haruno Yukinoshita used cursed power, it was like using a scalpel: complex and precise.
“No, no, no. How could an ordinary miko like me be that powerful? To seal a Progenitor? Even if all the Demon Slayers in Japan combined, they’d struggle, don’t you think?”
“Then what is this mask actually for?”
“It’s for Yuzuru and Kaguya.”
Hikigaya’s gaze changed in an instant.
Under the cold moonlight, his scarlet pupils bloomed—like a case of severe pink eye.
The pressure in that moment was so heavy the air itself seemed ready to condense into water.
Those two simple children, who were practically an endangered species—Hikigaya could not accept anyone having the intention to harm them.
“So scary, so scary.” The smiling, black-hearted miko said she was scared, but her body didn’t retreat an inch.
There was no fear to be seen at all.
“I’m a good person,” Haruno continued, her smile unchanged.
“Or rather, I’m a great benefactor to the Yamai Sisters. Even the seal that prevents them from going berserk now—I gave that to Shizuka.”
“By Shizuka, you mean Hiratsuka-sensei?”
“Yes. Back then, to prevent those two children’s power from triggering a spacequake, Shizuka used the sealing technique I created—’Separation and Reunion of Two’ —to completely seal the power belonging to the spirits within those two children.”
So that was it.
Yukino Yukinoshita.
Shizuka Hiratsuka.
The Yamai Sisters.
Haruno Yukinoshita.
This seemed to perfectly connect all the relationships between these people.
At the very least, he could determine that this woman claiming to be Yukino Yukinoshita’s sister was not an enemy.
“So is there a problem with the seal now? Do you need my help to reseal it?”
Hikigaya toyed with the mask.
He didn’t quite understand what use he—a complete layman when it came to sorcery—could possibly be.
But if the Yamai Sisters truly needed his help…
He would definitely help.
Those two children were already his friends.
“To be precise, it’s not that there’s a problem with the seal.” Haruno Yukinoshita’s expression finally grew more serious.
“It’s that the Yamai Sisters themselves have a problem. How much do you know about those two children—Yuzuru and Kaguya?”
“Not much.”
They were friends.
He knew they were spirits.
But to be honest, Hikigaya had known the Yamai Sisters for a very short time.
He didn’t know their background at all.
“Spirits are beings born with the ability to manipulate certain powers. The Yamai are spirits who manipulate wind. Originally, there was only one Yamai.”
“However, when she manifested in this world, an accident occurred. The spirit known as Yamai split into two individuals: Kaguya and Yuzuru.”
“That child Kaguya has chuunibyou. She always maintains an arrogant, aggressive attitude and uses theatrical phrasing. But that’s just her trying to appear dignified.”
“As for Yuzuru, her way of speaking is very quiet, and she has a verbal tic of adding agreement or criticism at the beginning of her sentences—”
“Wait.” Hikigaya interrupted.
“Isn’t that backwards? The Yuzuru and Kaguya I know aren’t like that at all.”
He paused.
“You’re very clever.” Haruno Yukinoshita nodded.
“The seal I created is called ‘Separation and Reunion of Two.’ The principles are quite complex, so I’ll spare you the details. You can understand it as a technique that uses the energy generated by the intertwining of two souls to seal a spirit’s runaway magical power.”
“Originally, the side effects of using this technique were nothing major. The two people whose souls intertwined would simply feel a deep closeness to each other—but they would remain independent individuals even with their souls fused.”
“But because Yuzuru and Kaguya were originally one person…” Hachiman Hikigaya frowned.
“Did something go wrong after their souls fused? Did it cause their personalities to become chaotic as well?”
He understood so far.
But if that were the only issue, this woman calling herself Yukima Miko wouldn’t have come looking for him personally.
“It’s worse than that.” Haruno’s smile faded another degree.
“If the continued fusion of their souls isn’t stopped, one of them will eventually devour the other. Or both will vanish entirely, and the spirit Yamai will be reborn.”
“What can I do?”
Hikigaya didn’t doubt that Haruno was lying.
Matters like this could be verified by asking Hiratsuka-sensei.
There was no possibility she’d tell a lie he could so easily expose.
He was only concerned with what he could do now.
“I thought about improving the ‘Separation and Reunion of Two’ technique by adding a new soul as a medium to separate Yuzuru and Kaguya. I called it ‘Separation and Reunion of Three.'”
“But I found that to be completely wishful thinking. The power of three souls is genuinely difficult to balance. So I abandoned that plan.”
“However, I have a new idea.” Her eyes gleamed under the moonlight.
“The ‘Separation and Union Parasitic Sealing Art.’ By attaching the souls of Yuzuru and Kaguya to a soul that is more powerful—powerful enough to completely separate them—the energy of the intertwined souls would be enough to seal the Yamai Sisters. At the same time, because they’d be blocked by a more powerful soul, there would be no need to worry about their souls devouring each other.”
“I see.” Hikigaya nodded slowly.
“The help I can provide… is that the Progenitor’s soul is powerful enough to be used for the technique.”
“That’s correct.”
“So the ‘Separation and Union Parasitic Sealing Art’ is inside this mask?”
“That’s correct.”
“Then what are we waiting for?” Hachiman Hikigaya didn’t hesitate.
“Let’s go to Hiratsuka-sensei’s house right now.”
If Haruno was lying, a quick check at Hiratsuka-sensei’s house would expose her.
If she was telling the truth, then saving lives was like fighting a fire—arriving a second earlier meant reducing the risk of the Yamai Sisters vanishing by a second.
But Haruno Yukinoshita grabbed Hikigaya’s arm.
Her expression turned grave.
“Before we go,” she said quietly, “have you prepared yourself?”