Eiji Usatsuka (?? ???, Usatsuka Eiji, born August 16 in Osaka Prefecture, Japan) is a Japanese light novel illustrator.
He is notable for the illustration for the series Zero no Tsukaima.
He illustrates insert images for many novels.
After university graduation he was employed as illustrator by the visual novel publisher Visual Art's using the pseudonym Sawagani (????, Japanese Freshwater Crab).
As side job he made illustrations for light novels which is against the company policy.
The similarity of "both peoples" designs, were however noticed and later revealed by Toya Okano (scenario assistant for Visual Art's' Clannad) in a Dengeki G's Magazine interview article presenting Visual Art's brand Mana’s game Angel Magister.