Prologue

A provincial city, predominantly serving as a bedroom community for the nearby metropolitan area, nestled among mountains on three sides.

Kawai Yuuma had a friend he’d known since kindergarten, someone he’d been stuck with through thick and thin—Kuramoto Kousei.

They’d race their bikes around the neighborhood, play kick-the-can at the park, compete to see whose shoes they could throw the farthest, and make mud balls together.

Behind the forested shrine, they’d catch bugs and build secret bases. At home, they’d play video games. Whatever they did, they did it together.

And there was one more person—a girl who would always tag along behind Yuuma and Kousei, sometimes running them ragged with her ideas.

『Hey, I heard there are crayfish in that irrigation canal over there! Let’s try catching some!』

『Hey, hey, want to race to see who can gather all these materials first in the game?』

『I bet there are Tsuchinoko in that shrine forest!』

She was Kousei’s younger sister by one year, Suzuka.

Suzuka, too, had grown up right there alongside Yuuma and the others.

They played everywhere together, got into mischief, got scolded, got hurt, and sometimes failed at things.

They were close enough to know everything about each other—the good, the bad, and the embarrassing.

To Yuuma, Suzuka was irreplaceable, and she probably thought of him as another brother.

They had an unshakeable bond, and back then, they innocently believed their relationship would stay that way forever.

The first time he noticed a crack in that belief was at Suzuka’s middle school entrance ceremony.

It was obvious when you thought about it, but Suzuka was wearing a girl’s uniform.

Yet somehow, Yuuma found himself muttering words of surprise.

『Suzuka’s wearing a skirt.』

『Surprising, right, Yuuma? Turns out Suzuka was actually a girl all along.』

『I feel weird about it too… Can’t I wear track pants underneath?』

『At least endure it for the entrance ceremony.』

『Yeah, I guess…』

Until then, he’d never really thought about them being male or female.

Looking back, that was the moment Yuuma first became conscious of Suzuka as a member of the opposite sex.