not familiar with her dazai specifically, but this is a character who is rescued from a suicide attempt via drowning in the first episode and his response is to get pissy at the one who saved him. this aspect of his personality gets toned down and more or less dropped entirely as the series goes on, and aside from his bandages, any incidences of self-harm (beyond literally putting himself in danger as a mafioso) are never actually addressed. a lot of players tend to play these aspects of the character up, but ultimately, it's very ic of dazai to treat these things flippantly. if anything, it'd be ooc for him to treat them seriously.