Thinking about a Reverse!AU of Twisted Savior Complex where Keiko lives, but Kaito dies (Because I can't imagine Keiko pulling the same stunts pulling Kaito did to keep him alive). Dazai comes up the mountain and Keiko convinces Dazai to take her with him. (Because of his ability that he reveals to her. I want them to have a sibling relationship. Because I firmly believe if Dazai met Keiko before the Plague hit her he would generally see what Kaito in fact saw in her, not that Keiko didn't have any flaws. Which I'm excited to reveal as the chapters go on. Because Kaito just talks and thinks about her. But he's only seeing her through a colored lens and refuses to question the things she does and says. Not that she's way worse than Kaito). Dazai and her would have the somewhat healthy relationship Kaito and Keiko were to have meant (because Dazai is Dazai). I feel like Keiko's place in the story will either be in the lower ranks where she meets Odasaku or take Higuchi's place (love her she still exists in this universe). But unlike Kaito she's not suited for this life and is not going to be that close to Mori like Kaito was. So she leaves the Mafia. She leaves when Double Black is practically at its peak. Dazai is confused. Wondering why she left him (he still has Odasaku, but he can't help that bitter feeling. Because where Oda was like a friend. She was generally like an older sister to him) . She works underground for a while until she meets this female doctor (*cough Yosano) and joins the ADA as a desk worker.
I was thinking about her having an ability. Maybe. But if she was it would be an extreme future sight (which is ironic considering Oda) but she literally can't tell if it is past, present, or future. Because they come to her at random times and could happen from a span of a second to like ten years ahead. It gets under control because of Fukuzawa (I think that's his name ability) but they still feel like fever dreams to her.