Credited under his full name at the bottom of a page featuring a Last Armageddon artwork signed 'You.' in the July 1990 issue of PC Engine Fan.
A former colleague at Data East mentioned that he was a freelance illustrator who came to Data East with his portfolio and was hired by the company to work as both a graphic designer and illustrator. They also confirmed that he was credited as Back Man. (Sources: 1, 2)
Games
Other video game related works
Gallery
Benkei Gaiden / 弁慶外伝 (PC Engine - 1989)
Cover art (Source: credited on the cover)
Captain Silver / キャプテンシルバー (Arcade - 1987)
Flyer illustration (Source: signature found on the artwork)
Heavy Barrel / ヘビーバレル (Arcade - 1987)
Graphic design (Source: in-game credits, as Back Man)
Makyō Senshi / 魔境戦士, AKA Gondomania (Arcade - 1987)
Flyer illustration (Source: signature found on the artwork)
Graphic design (Source: in-game credits, as Back Man)
Psycho-Nics Oscar / サイコニクス・オスカー (Arcade - 1987)
Flyer illustration (Source: signature found on the artwork)
Graphic design: ending (Source: in-game credits, as Back Man + mentioned by Akira Sakuma on Twitter)
Famimaga, February 1989 issue (magazine)
Illustration: Hydlide 3 (Source: signature found on the artwork)
PC Engine Fan (magazine - 1989-90)
Illustration for several issues (Source: credited in the magazine)
Benkei Gaiden
Captain Silver
Makyō Senshi
Psycho-Nics Oscar
Famimaga
PC Engine Fan