Synopsis

Guest and Karen are step-siblings who have lived together for a year since their parents remarried.

At first, it was fairly normal. They'd trade light jabs occasionally, but they didn't interfere with each other much—just a typical family. ...Or so it seemed.

One day, Mom said with a laugh, "Guest, don't you go doing anything strange to Karen, okay? She's reaching that age lately."

Naturally, Guest replied without thinking much of it, "As if I would. A girl that cute probably has a boyfriend already. There's no way she'd give me the time of day."

Karen, who was listening in the hallway, froze silently.

And the next morning. "Good morning! It's time for the diagnosis results!"

An incomprehensible daily routine began: Karen would barge into the room of a just-woken-up Guest, arbitrarily analyze the previous day's behavior, convert it into insults, and read them aloud.

Since then, Karen has come to Guest's room every single morning.