Issei is a high school student of average height with short spiky brown hair, with two short locks of hair behind his head, and light brown eyes. Following his training with Tannin in Volume 5, he gained a more muscular and toned build.

While he has worn various outfits throughout the series, his most commonly worn outfit is the Kuoh Academy boys' school uniform, which consists of a blazer (more commonly black, although in other media is shown with a tinge of purple or grey, with white accents) over a white, long-sleeved dress shirt with black highlights with a black ribbon on the collar, matching black pants, and brown dress shoes. However, Issei's uniform differs in the fact that he wears a red T-shirt underneath his open dress shirt and blazer, and wears blue and white sneakers in place of dress shoes.  (I dropped the role cause of personal reasons)