Chuuya has never been in a relationship before and that's where he differs from Dazai. Dazai had a reputation among women and had plenty of flings, but he had never had a serious relationship. Still it does not change the fact that Dazai clearly already knows how to behave in a relationship with Chuya no.

His lack of experience in romantic relationships means that he has no experience in the more intimate aspects of relationships, it's pretty obvious, he's always been too focused on work and his responsibilities to even think about it.

Since the beginning of his relationship with Dazai, he has constantly teased Chuui for being so inexperienced. Chuuya himself was in no hurry to take his relationship with Dazai to the next level, because he had never had a relationship with a woman, let alone a man.

Chuuya could, for example, kiss Dazai and trust him enough to let him live with him and even sleep in the same bed with him.

Did Chuuya want more than that? He did, he wanted to try, but he didn't dare to make the first step himself.

So after he and Dazai were allowed to go home after a mafia mission, he decided that he should at least give Dazai a hint to make the first move himself.

After showering, Chuuya decided that he wouldn't hint to Dazai but just tell him straight up that he was ready to move the relationship forward.

"Tch,don't look it sound like you’re doing me a favor here."

Chuuya was nervous,he was able to talk to Dazai and he agreed. With all this Dazai was completely calm, Chuuya was a little jealous of his confidence, but that wasn't the most important thing right now.

"Just remember, if you hurt me, I'll kill you."