Aiyeeee Book!Dazai AU. And the end is happy with a good Chuuya! The only thing that's missing is a sequel, lol.
Also, Dazai - "How to find the pen": Send Atsushi around the city! Lol! "detective training!"

Another thing, the poor Agency members, they realize something's off (or at least, one or two of them does) but they... they don't know.

I wonder if Chuuya knows now? Chuuya armed with meta knowledge? lmao

My favorite part of this is everything. :3 It was hilarious.