Seventh floor of the apartment, Room 704.
When the sun finally rose from the edge of the sea, Nagisa Akatsuki at last returned home.
She gently and quietly opened the front door, peeked her head in to look inside the house, and then tiptoed in, looking just like a guilty thief.
Because the sun had just risen, the lighting in the house was still insufficient, dim enough that Nagisa couldn't see the state of the living room.
So, Nagisa cautiously turned on the lights, and was immediately startled.
"Ko-Kojo-kun?!"
Yes.
Nagisa saw Kojou Akatsuki.
Under the lights that brightened the living room, on the sofa directly facing the entrance, Kojou was sitting there.
His face was stiff, his eyes bloodshot, with clearly visible dark circles under them. His entire body radiated an aura of grievance and fury, causing Nagisa to involuntarily take a step back.
"...Nagisa."
Looking at his younger sister who hadn't returned all night, Kojou seemed as though he was about to vomit blood or burst into tears, as he slowly opened his mouth.
"Why didn't you answer your phone?"
"Why didn't you reply to my texts?"
"Why... didn't you come home all night?"
Kojou, as if he had gone completely insane through the night and had become mentally and physically exhausted, sounded hoarse as he spoke.
"Where did you go?"
This simple question filled Nagisa with fear.
"Um... Kojo-kun?" Nagisa asked weakly, "Are you angry?"
"Angry?" Kojou's face contorted into an incredibly forced smile. After a few dry laughs, he said, "No, I'm not angry. How could I possibly be angry?"
"Even if my sister stayed out overnight, and even if it was with a boy her age, I wouldn't be angry."
"So... it's about time you told me, right? What exactly did you do out there? What did you do with that bastard? What happened that made you stay out all night?"
Looking at Kojou, who was forcing a smile, whose eyes were vacant and bloodshot, Nagisa was completely terrified.
"Ko-Kojo-kun, don't get the wrong idea, okay? We didn't do anything bad..."
By the end of the sentence, even Nagisa herself had become unsure.
We didn't do anything bad, right?
We only drove off two delinquent demons, that shouldn't count as anything bad, right?
But did we really just do that? Nothing else?
Maybe something else did happen, and Kai-kun just didn't tell me?
With that thought, Nagisa's voice weakened.
However, she had no idea that her guilty demeanor made her words entirely unconvincing and directly snapped the already tightly wound string in a certain siscon's mind.
"I'm going to kill that bastard—!"
Kojou's eyes turned bloodshot, as if he had become a true Vampire Progenitor. He rolled up his sleeves, ready to charge out the door.
"Kojou-kun?!"
Nagisa immediately cried out and hurried to grab him.
"Don't be rash, Kojou-kun!"
"Let go of me! I'm going to kill the bastard who dared lay a hand on my sister!"
"It's not like that! You've misunderstood! Kai-kun didn't do anything to me!"
"You're even defending him?! He must've tricked you!"
"Listen to me first!"
"That bastard! Nagisa still has some time before she turns fifteen! She hasn't even graduated middle school yet! She's just a kid!"
"I-I'm not a kid!"
"What?! So you're saying you've already stepped onto the path of adulthood?!"
"Ah, no, that's not what I meant, I didn't mean that not being a kid meant that..."
"I'M GONNA KILL HIM—!"
"NOOOOOO—!"
And thus, the Akatsuki household in the early morning became exceptionally lively, enough to disturb the neighbors left and right.
In the middle of washing up, Kaiser heard the commotion, and the corner of his mouth twitched slightly.
"Now I definitely won't be able to clear my name, even if I jumped into the Yellow River."
Thankfully, Nagisa hadn't minded why he didn't send her home last night and instead brought her back to his own place, otherwise it would've been hard for Kaiser to explain.
"Well, this is actually kind of funny too."
Kaiser quickly stopped caring about the matter, continued washing up, and prepared to head to school.
He had already made plans with Nagisa that from today on, they would go to and return from school together, and except for going home, they would act together no matter where they went.
"This is the proper way for a Fourth Progenitor and his watcher to get along..."
Indeed, I've taken the heroine's route.
Reconfirming this once more, Kaiser left the bathroom and headed toward the door.
...
Kaiser didn't wait for Nagisa outside Room 704. Instead, he went downstairs first and waited for Nagisa outside the apartment entrance.
And so, Kaiser waited for nearly an hour.
Then... Kojou showed up.
"Take this!"
Charging out of the apartment door, Kojou looked like a King of Fighters with his rage meter maxed out, swinging a punch directly at Kaiser who was standing outside.
That punch was fast and fierce. Though thrown by an ordinary human high school student, it carried an aura that made it seem like even a strong and burly beastman might not compare.
Unfortunately, that fast and fierce punch was effortlessly dodged by Kaiser.
"Hmm? Isn't this Kojou-kun?"
As if he hadn't noticed Kojou's anger and that punch just now, Kaiser greeted Kojou with the same demeanor he had when they first met yesterday.
"Good morning. Heading to school too?"
That calm expression easily pushed Kojou's rage meter back to full.
"You've got the nerve to greet me?!" Kojou shouted, trembling with fury. "You kidnapped someone's sister for a whole night, and you dare greet me?!"
"This means you're mentally prepared to have a real fight with me, right?"
For that usually laid-back Kojou to be this angry, to become so aggressive, it could only be because it involved his sister.
And there was no doubt that Kaiser had stepped right on that landmine.
So, he let out a laugh, both amused and helpless.
"Don't say it like that. I'm just happy to be getting along well with a classmate's sister."
As soon as those words came out, Kojou instantly exploded.
"How dare you say that...! Take this!"
Kojou charged forward in a rage, launching a barrage of attacks at Kaiser.
And honestly, he wasn't bad. As expected of someone who used to be on the basketball team, his agility was leagues above the average high schooler.
Kojou had once been the star of the basketball team. None of his teammates could keep up with him, which is why he was ostracized and ended up quitting the team.
Now, with his anger unleashed, he was fighting with quite a bit of force.
Unfortunately, while he had some presence, it wasn't enough.
At least, not for Kaiser.
Kaiser simply retreated and sidestepped at will, easily dodging Kojou's full-force "turtle punches."
Then, when Kojou threw his eleventh punch at Kaiser's face, Kaiser not only dodged by sidestepping and letting the punch brush past him, but also quickly extended his hand and sharply tapped Kojou's elbow.
That one tap caused Kojou's punch to veer off course, and he lost his balance.
CLANG!
With a crisp sound, Kojou's fist smashed into the nearby signboard.
"OWWW!"
Kojou immediately clutched his fist and squatted down, crying out in pain.
"You okay?" Kaiser also squatted beside Kojou, speaking with a seemingly concerned tone, "Why were you so careless? Next time try to aim better before you punch, okay?"
As he spoke, Kaiser poked at Kojou's reddened, swollen hand, causing him to hiss in pain.
"Y-You bastard...!" Kojou quickly backed away from Kaiser, shouting with teary eyes, "Just because you're good at fighting, don't think I'll let you off!"
"Such deep resentment, huh?" Kaiser raised an eyebrow and said with a smile, "It's just your little sister staying over at the neighbor's house for one night. Is that really something to get so worked up over?"
"You've got the nerve to say that?!" Kojou was so mad he laughed, raging as tears welled up in his eyes, "Nagisa's just a middle schooler! You beast! How could you do that to her?!"
At that, Kaiser finally understood.
So Kojou had no idea that while Nagisa did sleep over at his place, nothing had actually happened between them.
Most likely, he thought his sister had already been completely defiled by Kaiser, which is why he got this worked up.
Well, it made sense. A girl spending the night at a boy's place, not returning home all night, unreachable by phone, ignoring texts, just the two of them alone—it would be hard to believe nothing happened.
Nagisa may have explained, but the agitated Kojou probably didn't listen.
In that case, Kaiser had no intention of explaining.
"Oh? So you do know Nagisa's just a middle schooler?" Kaiser said with a faint smirk, "Then whose middle schooler is doing nearly all the housework at home, has no parents, and rushes home every day to cook for her big brother and take care of him?"
Kojou instantly froze and was speechless.
"In the end, the reason I was with Nagisa last night is kind of your fault, right?" Kaiser continued to twist the knife. "She's someone who usually goes straight home after school and even has club activities. Why should she have to go home and cook for you?"
"If you'd just made dinner last night, Nagisa wouldn't have lost track of time and ended up going out to eat with me."
"I'm new here, unfamiliar with everything. I didn't even know where to find a decent meal. And you, my deskmate, a member of the Going-Home Club, didn't show me around at all. In the end, your kind-hearted sister did it, and now you're blaming her instead."
"What kind of logic is that?"
Kaiser's blend of sophistry and twisted reasoning left Kojou on the verge of questioning his own existence.
Could it be... the one who was wrong... was me?