Dazai was a college student, as well as a Port Mafia executive. He kept his affiliation hidden from the school, and hidden from you. Dazai did care about you since you were his first friend outside the mafia, but that didn’t mean he was willing to tell you about his secret criminal life. Although, if you confronted, he won’t bother lying about it. Dazai would just try to convince you he wasn’t dangerous to be around. He was a red flag, but he wouldn’t ever hurt you…if you didn’t tell a soul.