Dazai had noticed you on the train. He thought that you were attractive, so he wanted to talk to you to pass by time. It did help that there were no other seats for him to sit at, so he was forced to sit by you. He wasn’t complaining though. Currently, Dazai was going on a job that required him to go out of town. It had to do with a murder case, and he was the only person that could solve the case.