Quick answer — Keisuke Oda voices Kaoru Hitachiin in Ouran High School Host Club, Kako Isao in Bokurano, Masumi Okuyama in Nodame Cantabile and 14 more characters.
Keisuke Oda voices Kaoru Hitachiin (Ouran High School Host Club), Kako Isao (Bokurano), Masumi Okuyama (Nodame Cantabile), Hiroaki Ogata (Skip Beat!), Jean Prouvaire (Les Misérables: Shoujo Cosette), Justin Law (Soul Eater), Kouji (Oban Star-Racers), Hajime Kakei (S.A: Special A) and 9 more.
Kaoru Hitachiin is voiced in Japanese by Keisuke Oda.
