This is mostly my own personal interpretation, but it is a very long ramble about me reading into Dazai's borderline personality disorder traits (abandonment, identity, dissociation, self risking behaviors, chronic emptiness, etc) or at least what I interpret as such. I do think ASPD is also a strong contender for Dazai, but I have yet to research that more in depth.
I think fear of abandonment being a trait he fills is best exhibited with Dazai and how he is with Oda. He clearly struggles with the thought overall losing anyone and anything close to him, but it's also a repeated thing by his line where he isn't sad about losing Oda/Ango and what felt like at the time almost everything, because he expects it. He fights hard for Oda to not go fight Mimic because he is afraid to lose one of his greatest friends, and who I think was also a favorite person in a way, but I don't explain that here.
He also fights hard for the agency yes because he cares about them, but I would argue it's also motivated in a similar fashion to not wanting to lose it/the people he cares about.He even puts forth an extreme effort of keeping up a persona as a means to not lose it. He even puts forth an extreme effort of keeping up a persona as a means to not lose it. Constantly joking around and not allowing much personal connection, at least as far as letting his true intentions or his personal thoughts go.
He also shows struggles with stable personal identity. Dazai views himself as something other than human in general. And also connecting to the heavy dehumanization themes around him, especially during his PM days. Dazai put on the persona of a "Demon Prodigy" and fit himself to that in what I would argue is almost a self sabataging way. He exposed himself to the worst to see and possibly feel raw humanity. And possibly gain a purpose or want to live, as well.This also is an example of chronic emptiness for Dazai and his search for a purpose to live.
There are a lot of examples of this for Dazai, obviously his biggest thing is suicide and constantly getting himself into those harmful situations. He also is shown to be a functioning alcoholic.yet being unable to fill the hole, which leads into suicide and Self harming behaviors. There are a lot of examples of this for Dazai, obviously his biggest thing is suicide and constantly getting himself into those harmful situations. He also is shown to be a functioning alcoholic. Physical self harm is really just a speculation, however I think it's a realistic thing to consider, and personally I do believe that.
Probably the biggest example of Dazai and dissociation/depersonalzation and loss of contact with reality is this scene in BSD 15. At least this is how I read it. There are other examples I think, one being the fact that I believe him disconnecting himself from his "humanity" is a form of it.
I also think that Oda is sort of a favorite person for Dazai. This is exemplified by the extreme lengths Dazai tries to go to in order to not lose him (dark era, beast), but also the extreme importance of Oda as a figure for Dazai. Despite never getting very personal, as stated by Oda himself, Dazai still has a strong attachment to him because Oda was arguably the first good influence in his life.
I definitely have a lot more thoughts on this, but this is just a shortened version and small ramble on some of the ways I read Dazai as implied/coded(?) BPD.
1) the force awakens is really good you should all go see it
2) spoiler not spoiler my Killjoys bae Hannah John-Kamen surprised me by being in it and even had a speaking line to grace me with her accent so there’s that
3) Rey and Finn are my precious children and i love them
