Kōji Seto (瀬戸 康史 Seto Kōji) is a Japanese actor and singer. He played the role as Wataru Kurenai in Kamen Rider Kiva. Through his role with Kamen Rider Kiva, he was also the lead vocalist of the J-Rock band Tetra-Fang. He reprised his role as Wataru Kurenai for the first and last episode of Kamen Rider Decade, as well as the Decade portion of Kamen Rider × Kamen Rider W & Decade: Movie War 2010. As of OOO, Den-O, All Riders: Let's Go Kamen Riders, Kiva was voiced by replacements in later appearances.