I will never let go of how Dazai's connection to the former boss is the most we know - and probably will know - about his past, his life "before" mafia. I'm putting it in quotations because it is very, very obvious that he had some associations with mafia even prior meeting Mori.
before reading the manga, the reasoning behind Mori choosing Dazai as a witness to the past boss' death and his "last sentiment" always confused me - why would the higher-ups of such a powerful and devoted organization give a shit about the words of some random child? why would his, specifically his witness would be enough to convince them to trust Mori, who was previously interviewed with mafia himself, but was not named a successor? Just because Dazai, on Mori's words, happened to be there and seen it? Mori didn't even know Dazai literally to the day he killed the last boss, so why him? it is abundantly obvious that the opinion of a person not related to the mafia in the first place would not be even considered as deserving attention.
for a fourteen year old Dazai's witness to be important, he has to be known for not just having relations to the organization, but to the boss specifically, and the type of relations he needs to have are personal. the people Mori wants to convince have to know Dazai - or, more likely, know of him, and they have to believe in Dazai's loyalty to the old boss, not to betray his last words. it becomes so much more clear that Dazai knows the old boss personally after reading the manga - one of the first scenes we get in the age 15 is Mori and Dazai talking in his cabinet a year after the change in leadership, and there is a one specific moment where Mori says: "there are some people who must never be allowed to rise from the grave", and Dazai repeats those words back, while there is a dark presence in the room between them, a presence of someone both of them knew personally. when the next thing Dazai says is: "I suppose there is no one I can rely on but you", I would argue is mirroring how in the past, Mori was the only one who Dazai could rely on th stop the old boss.
When later in the same arch Rimbaud ends up temporary resurrecting the old boss, there is a very, very unnerving dialogue between him and Dazai to happen. "Now there..," he says. "There is a familiar face". "Boy, boy", or, in another translation, "My child." "Has a doctor been picking on you?". There is an eerie tone to this question - it is asked in a way a trusted adult would ask a kid if his new classmates are nice to him, and we know he doesn't actually mean it, there is no indication that he cares about Dazai, so all is left of this question, is familiarity, something patronizing, posessive.
The old boss says, "Oh, how nostalgic. There is a face I haven't seen in a while" - and it is not something to be said to a stranger you barely seen a glimpse of, not something to be said to a person you even knew for a day. "As much as I like reminiscing of old times" - they knew each other, and they knew each other for a while. Before his mind even started deteriorating, maybe. At least months, years, most likely.
In this dialogue, Dazai calls him "boss", and later, "former boss", adding, "long time no see".
I haven't read it all in a long, long time, but somewhere there is also a moment, if I'm not mistaken, where Mori says, "I only begrudge the former boss for that man's life", talking, again, about Dazai.
Ah, anyway. Hate that anime doesn't enact it properly. Think more bsd enjoyers need to know about it. Asagiri will probably stay shady about it forever but at least we have some crumbs.
