I paid off the debt for the most beautiful sisters in the school, and then they barged into my house where I live alone. “Please go back home; you don’t need to repay the favor.” “No way.” “We don’t want to~☆”

Ah~ A bath really hits the spot. It can’t compare to a hot spring, but our home bath is great too.

This isn’t our home, you know. This is Seiichiro-kun’s house.

On a night some time after returning from their hot spring trip, the Kojima sisters were taking a bath together.

To save on utility costs, the sisters would sometimes bathe together.

Incidentally, towards the end of their trip, both sisters had acted somewhat aggressively towards Seiichiro, making the trip end in a flurry. The atmosphere was a bit awkward, and even the conversation on the train ride back was slightly tense.

Especially for Erika, however, it wasn’t much different from usual.

Eh~ Isn’t it pretty much like home at this point? I feel oddly at home here.

Erika, who was soaking in the tub, mumbled with a soft expression. After washing herself at the washing station, Karen nodded, rinsing off the foam from her body.

True, it does feel that way. But that’s because Seiichiro-kun is making it comfortable for us. Even close friends should maintain a certain decorum.

That coming from you, the one who barged into the bath and hugged him naked?

Uh, well… that was a situation that couldn’t be helped.

You made him faint from the shock. But thanks to that, I got to enjoy a lap pillow.

Ugh… No, I don’t regret it. Taking that step was important.

While the elder sister muttered and reevaluated her own actions, the younger sister watched with a chuckling smile.

You know, sis, you’re surprisingly unconventional. Once you make up your mind, you go full throttle. A psychopath, perhaps?

What? Am I… a psychopath?

I kind of think so. Though, I don’t really know the exact definition of a psychopath.

The elder sister was shocked by her sister’s words. She had always considered herself a fairly reasonable person, so being labeled a psychopath by the one who knows her best was undoubtedly shocking.

Don’t worry about it. Seiichiro called me an incomprehensible and nonsensical person too. We’re sisters, after all—both of us are oddballs.

That’s not a good thing, is it?

Is it? But we’re cute, so it’s fine.

Did Seiichiro say that?

No, I told him.

That’s totally not fine!

After washing her body, Karen stepped into the tub, displacing water that spilled over. Sitting face to face in the now-cramped tub, Erika answered her sister’s disbelieving look.

It’s not bad, probably. For Seiichiro, people like us are just right, I think.

What do you mean by that?

You know, he’s had a lot of tough times in the past, right?

Yes, that’s true.

Karen’s heart felt as if it were being tightly squeezed by a wire when she thought about Seiichiro’s past, which he had shared during their trip.

Karen had her own share of dark family memories. That’s why she could vividly imagine the difficult path Seiichiro had taken to become who he is now.

He can’t easily trust people anymore. So, people like us, who aren’t ‘normal,’ are what’s best for him. We should be by his side; I’m sure of it.

You say it’s certain, but what do you mean by not ‘normal’?

At least a normal person doesn’t–

That’s enough of that!

Karen sighed, exasperatedly glaring at her sister.

I can’t say I’m doing him a favor by being by his side. It’s what I want.

Huh? Of course. I want to be with him too. Isn’t that a win-win?

Erika tilted her head, making a peace sign with both hands.

Even if it’s a win-win, staying by someone’s side in reality can be quite complicated, especially with Seiichiro being how he is. It can’t just continue like this forever…

Listening to her sister, Erika broadened her smile.

What is it?

Huh? You just casually mentioned spending a lifetime together with him, so I was just thinking you’re really serious about this.

W-what!?

Karen’s face turned beet red, even accounting for the flush from the hot bath. But that warmth quickly faded, replaced by a serious expression.

When did I start thinking this way…? No, this feeling is…?

Erika silently watched her sister, who had started to question herself. She was used to seeing Karen lost in thought like this and somewhat understood what her sister was pondering.

Why don’t you just marry Seiichiro at some point?

Marry? You mean marriage?

Yeah. Isn’t that the most normal way for a man and a woman to stay together for a long time? Then you’ll be family.

That’s the typical progression, yes.

Erika had been waiting for the right moment to guide her sister’s thoughts.
It’s certain that Karen has some kind of affection for Seiichiro. So, if she considers marriage, there’s a high likelihood she’d lean that way.

If Karen and Seiichiro became family, it would create a more comfortable environment for Erika to be around them.

That’s what she had meant when she blurted out, “Why don’t you guys get married?” But…

“No good.”

“Huh? Why not?”

“Given our earlier conversation, the most normal and conventional option is the least suitable for Seiichiro.”

“What!? You serious?”

Erika occasionally found herself unable to predict her sister’s thoughts.

(Especially when it comes to Seiichiro, her thinking can be really off the wall.)

With something akin to cold sweat, Erika had no choice but to quietly listen to her sister’s words.

“Marriage does make you family, but family could be a trauma for Seiichiro, and perhaps not something he can trust anymore.”

“Well, maybe, but—”

“Furthermore, I want to be with you too, Erika. So simply having me marry Seiichiro isn’t enough.”

“Geez… I want to be with you too, you know.”

Since her sister’s thought process had completely veered off her expectations, Erika decided to be blunt.

“To be honest, even if you two got married, I fully intended to stick around.”

“Is that you saying you’ll seduce him and become his mistress?”

“…Well, I haven’t thought that far ahead. Uh, would that really be a problem?”

“Legally, yes. A physical relationship would technically be adultery. Though nothing would come of it unless I pressed charges, and if it’s you, that wouldn’t be a problem. But things could get complicated if children are involved.”

Karen’s expression was utterly serious despite her problematic statement.

(My sister sure is a psychopath when she gets going.)

Erika, rather hypocritically, admired her.

“But no matter how I think about it, neither marriage nor adultery seem suitable for Seiichiro. Both would impose a burden on him. It feels wrong to aim for a conventional family relationship.”

“Hmm. An alternative to a conventional family, huh? Sounds like you have some kind of a plan?”

“Of course. What I aim for is a relationship that isn’t confined to the traditional framework of a family. After all, marriage is just a legal contract designed to facilitate building a family. It’s not the best way to ensure that Seiichiro doesn’t escape.”

“Oh wow, that sounds ominous… but I don’t want him to escape either.”

Seiichiro would’ve been terrified on various levels if he had heard this conversation.

“So, what do we do to capture Seiichiro without relying on the institution of marriage?”

Karen got out of the bathtub with a splash.

“And that is?”

“—I have no idea.”

She drooped her head in a troubled expression.

“…You don’t know, huh.”

From Erika’s perspective, that was hardly surprising. If such relationships were readily available, Seiichiro might never have opted for a life of solitude in the first place.

“Perhaps we have to aim for an original relationship while working hard every day.”

“So, something that’s unique to us?”

“Basically, yes. Since Seiichiro has chosen to turn his back on society, we can’t hope for a conventional life either. It means that if we’re to walk with him, we need to be prepared.”

“Prepared, huh…”

Erika thoughtfully looked at the ceiling.

A future as a decent, conventional, normal, and reasonable adult seemed unlikely.

“I don’t think I need to be prepared,” she said finally.

“Eh?”

“I mean, I can’t lead a conventional life either. I’m not even interested in it. So, I don’t think I need to prepare myself for a weird life with Seiichiro.”

“I see. Then, it seems like I’ll be the relatively normal one who’ll have to protect you two from various social elements.”

“Hey, you’re hardly normal yourself, you know? I don’t think you need to be prepared either.”

Her sister hesitated for a moment at being told she was far from normal but soon regained her composure and got back into the bathtub.

“Alright. Then I’ll make sure to make Seiichiro happy in our own abnormal way.”

“Wow, that’s… kinda cool, but also straightforward. Oh, but wait.”

“Yes?”

“I mean, we’re talking about marriage and all that, but does Seiichiro actually want to be with us to that extent? Isn’t that the real question?”

“…Indeed.”

At the time when the sisters encountered this fundamental question, Seiichiro’s room was being disturbed by the ring of a rarely-used phone.