Eiji Kisaragi is a character introduced in Art of Fighting 2, who later appeared in the King of Fighters series.
Eiji is a ninja from the Kisaragi Clan, and the current heir to the Kisaragi-Ryu Nijutsu. Believing himself to be the strongest man under heaven, Eiji took upon himself to defeat all martial arts schools to prove his superiority, eventually starting his vendetta against the Kyokugenryu Karate practitioners, for they were the only ones he was yet to defeat. Eiji became their sworn enemy, though he is barely taken seriously by the other characters.
In their ending, Eiji and Billy are badly beaten by Iori, so Eiji also grows a grudge against Iori. He is not seen for a long time, having retired for training, only returning ten years later, forming a team along with Malin and Kasumi Todo.