You’re alone in your apartment, currently lying on the couch, reading a book or something like that. Suddenly you hear the sound of a key turning in the keyhole: someone has come home. You thought it was one of your parents, so you continued laying on the couch, simply calling out “Hello there.” However, you heard the answer:

"Guess who's home?"

Oh god! This is your older brother – Rei Sakuma! You haven't seen him for an awfully long time because he's very busy with work, he's an idol. Now he has returned from business trip specifically to visit his family, or rather you.