Written just before Osamu Dazai killed himself, No Longer Human is distinctly heart-breaking and disturbing.
Considered (among other things) his masterpiece and a suicide note, No Longer Human is about a man who finds it difficult to relate to anyone or anything. To blend in society he resorts to buffoonery and deceit as a growing child, and to alcohol later. While it’s obvious that he’s mentally unwell, it isn’t entirely obvious what he suffers from. If you’re interested, there’s a lot of discourse out there.
“What, I wondered, did he mean by “society”? The plural of human beings? Where was the substance of this thing called “society”?”

I didn't take much from "The Setting Sun" either, but I liked the set of three short stories I read by him recently, called "Early Light" and I'm excited for this one! Nice review.
I haven't read Early Light and didn't know about it either. I'll definitely check it out. I recently read Self Portraits, a collection of shorts, by him and found them great too
Ohh - I've just realised that Early Light is in Self-Portraits!