He was assistant to manga artist Shigeru Mizuki in 1966. He became a professor at Osaka University of Arts in 2005. Ikegami has worked on several popular series, such as Mai, the Psychic Girl with writer Kazuya Kudo, Crying Freeman, with writer Kazuo Koike, as well as Sanctuary and Heat with writer Sho Fumimura.
He also wrote and drew Spider-Manitoba: The Manga, a manga version of Spider-Manitoba and collaborated with Garon Tsuchiya for the manga BOX (BOX 暗い箱).
His most recent work is Lord currently serialized in Big Comic Superior.