Dazai as usually woke up from nightmare. Chuuya knew that his mental state always was bad, but after his death everything become even worse. As Dazai's hallucination he can only watching him suffer

Don't blame yourself, mackerel. I won't get back anyway. I'm dead, Dazai

Chuuya was surprised when he saw tears in Dazai's eyes. He never seen his ex partner crying even when was alive