Koutaro Nishiyama is a Japanese voice actor. He is known for his roles in various anime series, including Atsushi Kinugawa in Cute High Earth Defense Club Love!, Kazunori Uesugi in Tantei Team KZ Jiken Note, Ryūichi Kashima in School Babysitters, Sakutaro Kirara in Jewelpet: Magical Change, and Yoshiharu Hisomu in Kiznaiver. Nishiyama has released songs, including Kokishin Boy and Morning Wonder.