Ah. So it's that type of friend. This sort of job that doesn't always draw a line-- You did what you thought was best. It's not really your fault he can't see it-- does he really sound like that?!

(at this point, it's a little unclear whether dazai's talking to himself through peter, or whether it's genuine thoughts. he had himself been betrayed, a man whose morals are rotten like his own had been couldn't forget nor forgive a man's death, the line could have been drawn, but it hadn't been, and a traitor he became for deserting.

so, he gets it, really. and this is exactly why he's pouring more poison to himself, and carefully taking peter's beer glass to replace with what he's been drinking.)

There, there, buddy. You deserve the good stuff.