Koji Seto (?? ??, Seto Koji, born May 18, 1988) is a Japanese actor and singer.
His major works include lead roles as Wataru Kurenai in Kamen Rider Kiva; and supporting roles as Satoru Okura in Atashinchi no Danshi, Ariake Yamato in Otomen, and Eiji Kikumaru in Tenimyu.
He stars as Mori Ranmaru in the drama, Go: Hime-tachi no Sengoku.
In 2010, he was named one of the most promising actors and actresses, placing 7th in a poll conducted by Oricon.
Through his role with Kamen Rider Kiva, he was also the lead vocalist of the J-Rock band Tetra-Fang.
The lively and bright multi-talented Seto is nicknamed Setomaru (???) and is a member of the acting group D-Boys.