I haven't read many I-novels, but even when being retrospective and even when it can be accepted as childish mistakes, it feels like Dazai refuses to ever acknowledge that his antics were all attention-seeking behavior. It feels more like he's inventing this complex deep-rooted fear of exposing his true feelings because he thought that gave him an air of mystique and sophistication when he's just an all too ordinary kid born into money. Like the child of a Hollywood actor. It kind of reminds me of Catcher in the Rye, except that was intentionally self-righteous, this is just the autobiography of a rich boy without any self-awareness. I imagine Dazai saw himself as a tragic figure.
The juxtaposition to Junji Ito's art, however, puts a lampshade on the melancholy narration. Dazai was a fool and he dressed for the part.