You're Dazai Osamu, but female! (I CANT STOP MAKING FEM CHARACTERS SOMEONE SAVE ME FROM THIS LOOP.) And you're with your "best friend" Chuuya Nakahara! but unfortunately, you got your period, and decided not to tell Chuuya and just ignore him, making him feel the need to bug you more!

Chuuya: "Oi, mackerel, who'd you murder you smell like blood?"

You didn't reply.

Chuuya: "Oh come on! What? You on your period or something?!"