is a Japanese actor and voice actor who is a member of Haiyuza Theatre Company. He has done popular voicing roles in Hajime no Ippo, Utawarerumono and Kamen no Maid Guy. He is also known by the nicknames "Rikki" and "Riki-chan". Koyama become well known for voicing Yamato from Naruto, Kogoro Mouri from Case Closed and Coyote Starrk from Bleach.