WHO are YOU - A Story of a Middle-Aged George Akiyama

(from ebookjapan):
This is an autobiographical manga in which the genius George Akiyama makes himself the main character and asks himself questions as he relays various episodes. After leaving a cabaret club in Kabukicho, middle-aged mangaka George Akiyama mutters in his mind, "I killed my wife." Later, surrounded by yakuza, Akiyama fights back by using a key chain with a bunch of duplicate keys to his mistresses' rooms as a weapon. ......!

A work in which Akiyama reflects upon his life and career, many characters from his previous works - such as Derorinman and Futaro Gamagori - make guest appearances.

Note: The original release was a single volume, but the digital release split it up into 2 volumes.
A bonus chapter featuring Akiyama reflecting upon The Moon was done as part of Weekly Shonen Sunday's 50th anniversary special My Sweet Sunday. As it was done post-serialization, it is uncollected.