Amazon is listing a print release of Shintaro Kago’s Dementia 21 manga from Fantagraphics Books. The volume is is listed with an August 28, 2018 release date, and is supposed to be 300 pages.
BookLOUD serialized the manga in English and Japanese in its bilingual ComicLoud digital magazine until the magazine ceased publication in 2013. BookLOUD also released four volumes digitally in both English and Japanese, and a total of seven volumes in Japanese.
As of this writing, there has been no confirmation from Fantagraphics Books as to whether or not this listing is accurate.