AlmightyX10
While in mission until brought him to Shinjuku, Dazai was found by someone in the river. Yes, he was in attempt to committed suicide again. He collapsed, and woke up in rest room at Almighty. He looked for the interrupter, dunno why, he ended up to replace that rescuer(or Dazai will more called him as interrupter) job as helper at Almighty. He known as, Hiruma Yoichi. Then, beside he usually at Yokohama works as detective, he is also a helper while he needed. And sometimes he will be seen at Almighty Headquarter while he's slacking off from his job as detective. For his preference, look at here.
Bungou Stray Dogs Gakuen AU
This setting is actually an alternative universe from official for April Fool, which Dazai is a highschooler that often hospitalized because his suicidal attempt, especially when final exam, making him always never graduated from school until three times.
BEAST
In short, first setting of this story when Akutagawa faced Dazai at first time. It was 4 years earlier from Dark Era. Dazai never be friending with Odasaku, taking Mori Ougai's place after he was killed from against Mimic, becomes a boss of Port Mafia instead of merely Executive. Soon it's revealed their world merely one of many pages of The Books, which is in the end, Dazai was finished himself to protect this world with Akutagawa and Atsushi, when Odasaku is alive only in this verse.