Itou is an advisor to the Shinsengumi who is later revealed to be a traitor whose ambitions were used by Takasugi in an attempt to destroy the group from the inside. He considers himself a rival to Hijikata and manages to get him suspended from the Shinsengumi, later attempting to assassinate Kondo. However, his plan is foiled by the members of the Shinsengumi and Yorozuya. After losing his left arm and being defeated by Hijikata, after which he begins to realize how important the bonds he formed in the Shinsengumi were to him and how foolish it was of him to try and betray his dear friends. He is allowed to have one last duel with his old rival and is allowed to die as a friend and a warrior.

Itou is roughly based on Itou Kashitarou of the Shinsengumi.