While working on a shounen manga, manga artist Usamaru Furuya comes across a website titled No Longer Human, an online diary created by a man named Youzou Ooba. Youzou describes his own life as one full of shame, particularly detailing his descent from a popular and high-ranking high school student to a slovenly-looking man with white hair despite only being 25 years old. Astonished and captivated by this rabbit hole of misanthropy, disconnection, and lust, Furuya decides to continue reading and eventually uses his artistic talents to chronicle the troubled man's autobiography.

Ningen Shikkaku is an adaptation of Dazai Osamu's novel of the same title, originally published in 1948.

The series was published in English as No Longer Human by Vertical from October 25, 2011, to February 28, 2012, in a left-to-right format. Kodansha USA later released a complete omnibus edition on November 1, 2022.