Kaoru was once a member of Kurei's Uruha, but later, he becomes a member of Recca's team in the Ura Butō Satsujin. He wields the Kōgan Anki, a puzzle-like weapon that has five different forms. In the manga, the weapon also has a mysterious sixth form: 'Mu' (Nothing). At the series end, he follows Kuurei to the past forever leaving his friends.