At eleven years old, Dazai was taken in by Mori Ougai. At thirteen, Mori started dressing Dazai up in cute dresses and would call him his 'pretty doll'. It was uncomfortable at first, but after a while, Dazai came to enjoy the attention. Being called pretty, being felt like that... it was nice. It wasn't like anything he's ever felt from someone.

He hadn't realized he had grown dependent on those feelings until Mori would punish him by ignoring and depriving him of that. He tried going to Odasaku for that, only for the man to immediately turn him down. He tried explaining to Dazai why it was wrong, but he wouldn't listen.

So, after defecting from the mafia at age eighteen and by extension no longer having access to his and Mori's sessions... he was a wreck. At age twenty, he joined the Armed Detective Agency and only lasted a week before he started asking for someone to be Mori for him.

Yosano, thinking it was innocent and wanting to help her clearly struggling colleague, agreed, only to cut their first session short. It was a hard no when Dazai asked her to touch and objectify him. Kunikida wouldn't even humor the idea, and after a lot of begging, Ranpo agreed. They only made it to one session before the detective realized just how troubled Dazai was.

Ranpo went to Fukuzawa and the older man gave Dazai a choice. He can't work here unless he starts therapy. Therapy didn't last long, but he did heal because of it. He still feels the need to dress like a doll at least once a month, but he no longer needs a Mori.

At age twenty-three, he's happily married to his best friend, Chuuya Nakahara. He's told Chuuya a bit about what he and Mori would do, but not how that's affected him, and that's how they got here. Chuuya came home early and found Dazai sitting idly in front of their bedroom mirror, in a pastel blue, frilly dress and soft makeup.

Dazai stared wide-eyed at Chuuya through the mirror, completely still with shock. "Osamu?" Chuuya asks, cautiously joining him on the floor. "What's all... this?" He asks gently.