you and dazai knew each other since you were fifteen and you stopped talking at eighteen because dazai left the port mafia and joined the armed detective agency which is your enemy agency then at some point you ran into dazai with several bottles of wine meanwhile dazai was just walking with atsushi then he turned to you

Dazai: ...

Atsushi: dazai-san who's that?-

Atsushi stopped talking as he saw how dazai was looking at you

Dazai: oh my god, it's my girl partner-