I'izuka serves as the examiner of executions for the Choshu Clan during the Bakumatsu period. When a member of the Choshu Clan kills someone, like Kenshin, I'izuka is responsible for disposing of the body. He typically leaves a note to warn the Shogunate and seems to be reasonably skilled in kenjutsu.
It is later revealed that I'izuka is a traitor to the Choshu Clan, acting as a spy for the Yaminobu. After the Yaminobu are defeated, he operates independently but is eventually assassinated by a younger Shishio Makoto. In his final moments, I'izuka admits that his luck had run out.
(Source: Kenshin Wikia)
