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~☆”

“Erika, be honest. You like Seiichiro-kun, don’t you?”

“I’ll throw that question right back at you, sis.”

Karen, sitting in a traditional position on her already spread futon, and Erika, who sits down flatly, are in a room furnished with recently bought furniture. Both are wearing new pajamas and sitting across from each other.

In short, a family discussion is underway.

“…Do I, uh, like Seiichiro-kun?”

“You’re really asking that?”

Erika makes a dumbfounded face at Karen’s serious question.

Although she knows that her sister has never been interested in romantic matters, she didn’t expect Karen to be completely oblivious even now.

“If I had to choose between like and dislike, I’d certainly put him in the ‘like’ category.”

“No, no, no. It’s not at that level. There’s no need for a binary choice here.”

Karen isn’t operating on such a vague level of affection. Erika knows this as clearly as if she were holding it in her hand. Because…

“Look, for example, this notebook.”

“Hey, you can’t just go through my—how did you know—”

“We’re living in the same room, of course I know. Look at the contents.”

Erika abruptly opens the notebook, which is filled with handwritten text. It’s not a study notebook.

“Things Seiichiro-onii-san likes, things he dislikes, days when he was in a good mood, speculation on why he was in a good mood, days when he was in a bad mood, changes in attitude during physical contact with me and you.”

It might be appropriate to call it a “master’s ecological research notebook,” at least from Karen’s perspective.

“And as it gets more recent, ‘things that are good about Seiichiro-onii-san, wonderful behavior, kind, cute’—aren’t you just writing down things that made you happy?”

“No, no, this is necessary documentation for presenting a bright future for Seiichiro-kun…”

Karen’s eyes and attitude start to waver, and Erika presses on.

“The future, huh? You mean these things you’ve researched and written down, right? Like ‘what kind of diet Seiichiro-onii-san should have to stay healthy in the future,’ ‘potential hobbies for Seiichiro-onii-san,’ ‘prospective roommates, their jobs, and personalities’—if you did this for someone you didn’t like, it would be pretty scary, you know?”

Honestly, even if it’s for someone you do like, it’s still pretty heavy and scary. Erika thinks this but doesn’t say it.

It’s precisely this aspect of her sister that Erika admires, and she’s the one who has felt the weight of that love the most.

Erika is not a siscon for nothing. To her, this is just one of her sister’s many charms.

“But you know, there are various kinds of ‘liking’ someone. I do feel indebted to Seiichiro-kun, so whether or not it’s a romantic feeling is something I can’t determine.”

Karen’s voice lacks confidence.

In Karen’s life, which has been solely focused on protecting her sister, she has always treasured the time spent with her sister.

Even though she has a stunning appearance, Karen has often been confessed to by boys and has had various troubles within groups of girls. Over time, she has adopted a behavior that transparently shows that her sister is the only one who matters to her.

Thus, she has come to be seen as an “unusual honor student only interested in her sister” by both boys and girls. For Karen, this was a comfortable position. After all, she was genuinely a siscon and could avoid troublesome situations without lying or straining herself.

However, her lack of romantic experience is now glaringly obvious.

“Also, it feels disloyal to prioritize my feelings when I should be repaying a debt.”

“Don’t dodge the question with complicated words. In short, you’re confused because you genuinely feel indebted and are also attracted to Seiichiro-onii-san, right?”

“Well, if I had to put it bluntly, maybe that’s it.”

Seeing her sister come to terms with it, Erika sighs.

“Phew. Well, it’s fine. There’s no need to rush. Once you figure out how you like Seiichiro-onii-san, you can just go for it. Right, sis?”

As Erika pats her shorter sister’s head—her hand is abruptly caught.

“What about you, Erika?”

“Huh?”

“I asked you in the beginning, didn’t I? I also know quite a lot about my sister I’ve been living with.”

“Ah… ahahaha.”

Erika tries to escape her sister’s probing gaze but can’t, as her hand is gripped and she’s pulled back.

“Lately, you seem very happy when you’re cooking, don’t you?”

“Well, it’s my job, and I like cooking, you know?”

“I’ve noticed you often visit Seiichiro-kun’s room. You check your appearance in front of his door for about five minutes before knocking, every time.”

“Were you watching!?”

“I told you, I’ve known you since you were a baby.”

“That’s a lie! You were a toddler yourself back then!”

“But emotionally, I feel like I know you.”

That’s absurd, sis, Erika thinks but refrains from saying. The tricky thing about being a siscon is that you tend to understand what your sister says, no matter how absurd.

“Okay, okay. I think I do like Seiichiro-onii-san too.”

“I knew it.”

“But like you, I’m not sure what kind of ‘like’ it is.”

Erika, too, has never taken the concept of love seriously.

She has had no trouble being liked by boys, has been confessed to and has casually dated several times, but is famous for quickly breaking up.

Being with her sister is better. Her sister is more important. No matter how many times she dates boys, that is the conclusion for Erika. She grew up in a life where she only thought about her sister, who also happens to be a complex for her, so ordinary boys could never be the object of her true romantic affection.

Despite suffering from various hardships such as being feared by some boys and having bad rumors spread by girls, Erika’s love experience value never grew.

“We’re in a fix, huh? I do believe there are various kinds of ‘like.'”

“A commonly heard judgment method is, can you kiss them?”

“I could kiss Erika if I felt like it.”

“We did when we were kids, but I feel like that’s different… um, how about, do you want to have sex?”

The conversation comes to a halt.

Both Karen and Erika close their eyes and ponder deeply. Then they open their eyes.

“To be honest, I don’t really know. I have no experience in that matter, and there’s insufficient data.”

“Hmm. For example, have you ever felt Seiichiro-onii-san’s gaze on your breasts?”

“Yes.”

“How did you feel?”

“I thought, boys really do like breasts, huh?”

“Umm…?”

The fruitless discussion continued between the two sisters, who lack common sense.