Kappei Yamaguchi (山口 勝平, Yamaguchi Kappei?) (real name: Mitsuo Yamaguchi (山口 光雄, Yamaguchi Mitsuo?)) (born May 23, 1965) is a male seiyū from Fukuoka, Fukuoka, affiliated with Gokū and 21st Century Fox. His blood type is B.
He is best known for the roles of Ranma Saotome (Ranma ½), Tombo (Kiki's Delivery Service), Yattaro (Kyattou Ninden Teyandee), InuYasha (InuYasha), L (Death Note), Usopp (One Piece), and Kaito Kid and Shinichi Kudo (Case Closed). His current starring roles include that of Raimon "Monta" Taro, the Deimon Devil Bats' ace receiver in Eyeshield 21.
He made his first public appearance in North America at Otakon 2008.