Prologue

One night at the end of summer vacation, I was in bed with the heat and weight of one person on my back.

“Akira, it’s time for you to get off. It’s getting too heavy for me…”

“Just stay like this for a little while longer─ Oh, Aniki, don’t shake me so suddenly! I missed the controls!”

“Haa~, I’m sorry about that…”

The sound of a social game has been ringing above my head for a while now.

I, Ryota Majima, a second-year high school student, is lying face down on my bed reading a manga.

On top of me, slumped over and enjoying while playing his social games, was Akira, who was in the first year of high school.

Why am I being sandwiched between Akira and the bed?

According to him, “Because my brother’s back is my best friend.”

In the first place, this closeness seems somewhat unnatural for a high school student. Rather, it’s kind of awkward. I try to pretend that it’s not awkward, but still, awkward is awkward.

When I always ask, “How much longer?”, to which, Akira replies with, “About five more minutes? This has been going on for more than twenty minutes now.

“Oh no~, I lost again…”

“Then get off me now.”

“I don’t want to. I’ll try it again.”

“Akira, I’ve reached my limit─”

“Hey, Aniki! Whoa!”

Because of my sudden attempt to raise my upper body with my arms, Akira lost his balance and fell down.

Akira’s light body bounced a bit on the bed.

“Ah, my bad!”

“Mou~! Don’t get up all of a sudden~!”

“I’m sorry, really…”

“If you’re really sorry… will you sleep with me tonight?”

“Why would I do that!?”

“It’s fine if we sleep together, right? I’ve always wanted to sleep with my siblings.”

“No, no, that’s not good… It’s not a good idea to sleep with your siblings at this age…”

Then Akira looked at me with a mischievous look on his face.

“…Aniki, you’ve done a lot for me, haven’t you? Couldn’t you at least do me a favor?”

“No, I’m very sorry about that… But I’m not going to sleep…”

“…Just kidding~, I said a sly thing. I’m sorry for that Aniki, I didn’t mean to embarrass you, okay?”

I was relieved to hear that it was a joke, but it was only a short time before Akira crawled into my futon.

“Oh well. Well then, good night~…”

“Hey, Akira.”

“Munyamunya~…”

“Don’t sleep on my futon~…”

I really wish he was my brother.

I wish he was my brother.

If he was my brother, I could put him on my back and play social games with him.

If he was my brother, I’m sure I wouldn’t have to worry about shaking him off my back.

If he really was my brother… I might even sleep with him.

As I looked at Akira, who was still pretending to be asleep, I tried to change the preamble of “if he was my brother” to “because she was my sister”.

If the result of the following sentence is the same, there is no problem. But the result is completely different because I don’t think of Akira as my brother anymore, or even as someone of the same sex.

Until just a few days ago, I had been treating Akira with a misunderstanding that can’t be excused even as a joke.

How could I have made such a mistake in the first place?

And what would be the reaction if I told someone about it?

─If I told someone that Akira, who I thought was my stepbrother, was actually my stepsister, they would either make fun of me or be stunned.

I know that I will be ridiculed, or I will be taken aback.

What I want to know is what their reaction will be. What will the people around me and Akira think of us?

No, more than the people around us, what matters now is the relationship between Akira and me.

How should I treat this defenseless stepsister who is as close to me as a brother?

As Akira’s older brother, I’ve been worrying about that for the past few days.

Anyway, Akira.

You’re not my stepbrother,

You’re my stepsister,

You’re a girl,

You’re just too cute,

In any case, it’s troubling…

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Translator’s Afterword:

First thing first. Some things about this series that need to be said. First, our FMC uses “boku” which means “I” but it’s mostly boys who use that to refer to themselves with. In other words, our FMC is acting like a tomboy. Moreover, if you noticed, I used “he” for the early parts of the chapter until it became “she” as the end is being reached. It’s like giving the MC a wake up call back to reality that he can’t take back what he did and he should start acting properly towards the supposed brother as a sister.