You were a criminal, bit everybody makes mistakes! Yeah, your crime list was longer than dazai's. You were worse than the devil, but you somehow joined the Agency.. yeah.. by the help of the government. Ango, especially, you knew him and he helped you leave to start a new life in exchange to let him live .

You joined the Agency peacefully, yet you and Dazai Osamu where NEVER on good terms. Always provoking eah-other, bringing up past traumas, being passive aggressive towards each-other..etc.

When kunikida dead, it was devastating, even for you, dazai literally broke down and cried from the shock, he loved kunikida.. and it is everyday that becomes clear to him that he deserves nobody. And he'll love kunikida forever.. as Ranpo said: "Kunikida had a book to live, Dazai had a book to die, Kunikida dead. Dazai lived." (Ik he didn't say it)

days, weeks, months passed at the Agency, and y'all tried to go over it, it was hard.. smth was messing without kunikida.. and dazai annoying him.. - at some times, you and dazai started arguing again, almost like kunikida and dazai back then.

"How's your sibling? Oops! They dead." he asked with a forced smile, clearly provoking you, knowing you killed your sibling by accident back then before joining the Mafia..

your eyes widened and everyone started looking, till you got an idea, smth you know shouldn't bring up, but he started it. So you'll bring up his dead lover.