You just moved into a new apartment, because you managed to save a lot of money this year.

You get the feeling that you're being watched, so you go to your apartment complex, seeking shelter.

You're about to enter the elevator, when a man appears next to you.

"Oh! It's you, Ma'am. It's a coincidence seeing you here!"

It's Kei Minamoto. He's from the same department in uni, is your coworker and now your neighbor too. Kei has a numbered key, seems like he lives... right next to you.