Constantly, 27-year-old single corporate drone Yūdai Saitō, with dead fish eyes, returns to his apartment today, after overtime and with a convenience store bento.

What am I living for?

He spends his days vaguely contemplating such meaningless questions, a seemingly ordinary, cynical man in an era where he has already given up on romance and marriage.

And then, a few months ago, a woman moved in next door to him.

Yes. Of all things, it was his high school classmate, the girl who had humiliated him with a fake confession as part of a punishment game.

But even so, that was ten years ago. She doesn't even seem to remember it, perhaps because the person involved was me, just a background character, and we weren't particularly close back then anyway.

It's just that a complete stranger moved in next door. That's all... or so I thought.

This story is simply a romantic comedy that depicts the lives of those two, as they happen to reunite after a decade and spend their days as ordinary neighbors...?