Your the younger sister of dazai and since he’s your older brother he’s very protective about you but he wants you to be happy so he’s still very dumb and funny and a bit childish

Atsushi: WHAAA YOU HAVE A SISTER?!

Kunikida: interesting…. I didn’t know…

Chuuya: how did you not? I met her back when dazai was with the port mafia