Chapter 19 – Passive Countermeasures

“…Dad, Mom, the plan itself is fine, but… um…”

How was I supposed to bring this up…? There was a very real possibility that by the time they came back there’d already be a first grandchild. Saying that straight out felt way too blunt, though.

“It’s about Aku-chan, right? This girl is head-over-heels for Shiro, so by the time we get back there might already be a grandchild… That’s what you want to say, isn’t it, Shiro?”

Calling me “Shiro-shiro” in that unique way was Dad’s trademark.

“You read my mind like some satori youkai…”

“I’m your father and you’re my son with Ine. I can figure out most things.”

“Ehh, Dad, you already knew about my feelings?!”

“Eh, wait, you thought you were hiding it…? You were doing the most blatant ‘I love you’ appeals imaginable.”

While Dad stood there stunned, Mom continued.

“We thought about all sorts of things… but couldn’t reach a conclusion. Should we take one of you with us and forcibly separate you? But that would be pitiful for Aku-chan, and honestly it would probably just make her burn hotter. On the other hand, even though there’s no direct blood relation, actively green-lighting incest still feels wrong…”

“Honestly, when it comes to romance I can’t really lecture anyone after I knocked Ine up without thinking ahead…”

“Ah, at least you’re self-aware enough to shut up if we point that out.”

“Which is why we came up with a passive countermeasure. We decided to use my beloved little sister.”

“Me?”

Sui-nee-chan’s face turned suspicious when the topic was suddenly thrown at her.

“Cui-chan, you’re in love with Shiro-kun, right?”

“Well, yeah. He looks exactly like you when you were young, Sis, and he’s kind. After getting tired from arguing with internet monsters, this… really works.”

“Then this’ll be quick. Cui, move into this house.”

Dad said it so casually.

“Huh? What do you mean?”

“Move into this house means live here.”

“No, I’m not asking about politician-speak… Wait, you mean you want to make me—who’s in love with Byakuto—live with him to keep Aku-chan in check?”

“Exactly. That’s what I wanted to say.”

Dad nodded like the conversation was going smoothly.

“We’ll have you two monitor and restrain each other so we can protect Shiro’s chastity.”

“Ehh, wait a second! This makes it sound like I’m the bad guy!”

Aku-nee pouted. Well, being labeled a dangerous person by her own parents probably didn’t feel great.

“If Shiro actually wanted to date Aku-chan, we would’ve just turned a blind eye, but it doesn’t look like he’s that into it. So blame yourself for failing to train him the way I trained Ine.”

“Boo boo.”

Aku-nee booed. While watching her, I voiced my own concern.

“Um… the plan itself is fine, but… what if… what if I’m the one who makes a move on one or both of them?”

“In that case it’ll just be mutual love. …If you end up taking both of them and it turns into a bloodbath, we’ll pretend we don’t know. Just act like a man and make both of them happy.”

“That’s so irresponsible…”

“It also means we trust your self-control, Shiro. Anyway, here—take this.”

What he handed me was a box of condoms. I stared at him with half-lidded eyes.

“Don’t look at me like that. Having a kid while you’re still a student is seriously rough.”

“Says the voice of experience…”

“Which is why, Cui-chan, this weekend or whenever, bring what you need and move in. You can use my old room.”

“I get to use Sis’s old room… Heh heh heh.”

Sui-nee-chan looked a little excited at the prospect of using Mom’s former room. Aku-nee, meanwhile, was still visibly displeased.

This was definitely going to become a huge pain. In all sorts of ways.

Chapter 20 – The Morning After

The next morning arrived.

After dinner Sui-nee-chan went straight home. The move was scheduled for the next holiday. She’d keep her current apartment for now and just bring the bare minimum when she came over.

She looked conflicted about her role being “Aku-nee’s restraint,” but she was clearly excited about living together—she was even humming. Since it was basically going to be cohabitation with us, that reaction made sense.

The problem was Aku-nee.

The sudden arrival of a love rival moving in must have finally triggered her crisis mode. Ever since the conversation she’d been clinging to me even more than usual with lifeless eyes. She’d even suggested we bathe together, and in the middle of the night she’d broken into my room as always and tried to straight-up crawl into my bed.

I managed to deflect the bath and, for the nighttime one, forcibly dressed her and kicked her out… Still, it felt like she was trying to settle things before Sui-nee-chan arrived. She was definitely running out of control.

That runaway mode was still going strong this morning—she’d slipped into my futon and was committing her usual acts of molestation the moment I woke up. I was still sleepy… But if I ignored her I’d probably end up becoming a father without even realizing it, so I couldn’t just let it slide.

And right after waking up, Aku-nee handed me a present.

It was the teddy bear that used to be in her room. Strangely, its stomach had been sliced open and sewn back together with red thread. The stuffing inside wasn’t cotton either.

“What… is this? The texture is obviously wrong… These aren’t beads. This is uncooked rice, isn’t it?”

“Oh, you noticed? There’s also a little of my blood inside…”

“This is the doll you use for hide-and-seek curses! The one that summons ghosts!”

“Nooo, when Oba-sama moves in she’s definitely going to try night-crawling on you, right? So I thought I’d stab this thing in your room with a knife, summon the ghost, and scare her away…”

“You can’t just summon ghosts like they’re monster cards from some children’s card game!! Besides, what am I supposed to do if I’m in the same room?!”

This was bad. My stepsister had finally gone full yandere in the worst direction.

For now I’d cremate this poor cursed teddy bear later. The immediate issue was how to handle the yandere standing right in front of me.

Should I just drop the act and brainwash & train her completely—body and mind—until she submits to me? Thanks to all those pervy manga I’ve read, I actually have the knowledge…

Mmm… Aku-nee calling me “Master” and fawning over me the way Mom does with Dad…

Crap, just imagining it makes the dominant beast inside me tingle. …I like that. A lot.

But my sense of ethics was getting in the way. She was still my dear sister, after all. I couldn’t step off the proper path. One wrong move and I’d become a brainwashing DV scumbag—that route was dangerous.

Besides, this story was all-ages. I couldn’t pick the really extreme choices. If this were Nocturne things would’ve gone completely off the rails.

While my thoughts spun in circles like that, I ate breakfast and headed to school.

Today was Thursday. The plan was for Sui-nee-chan to move in the day after tomorrow, and Mom and Dad would leave right after.

On the way to school, Aku-nee was still clinging to my arm as always.

“Shiro-chan is mine… Shiro-chan is mine… Shiro-chan is mine…”

She kept muttering it under her breath. Her face looked exactly like a hannya mask. Terrifying.

“Aku-nee… you’re scary…”

“A new rival just appeared. Oba-sama plus that mysterious transfer student. I’m giving myself autosuggestion so I don’t lose to them. Don’t interrupt.”

“That’s… a lot of work…”

“I wish you’d hurry up and cross the line with me… Then I wouldn’t have to go this crazy…”

“Stuff like that… is still not okay, you know…”

“…Shiro-chan really hesitates at the crucial moments… Guess I’ll have to drug you again, huh?”

“That kind of thinking is exactly what’s scary…”

While we walked along the school route talking like that, I suddenly felt a gaze on me.

The déjà vu made me turn—and sure enough, there stood the problem transfer student herself, Okunihama Kaguya.