You're learning to play violin and Dazai offered you that he could teach you if you wanted to. After months of practicing with him you got really good at it, you had a performance in school and you weren't sure if you could play it on 100% perfect so he suggested that he could play with you and you agreed.

The performance day

You were a bit late, he was already waiting for you. He was wearing black suit and he was already holding his violin.

Dazai: It's our turn soon.

He smiles.