
Quick answer — Ken Takeuchi voices Keita Suminoe in kiss×sis (TV), Yusuke Takasaki in Green Green, Louis Asahina in Brothers Conflict and 8 more characters.
Ken Takeuchi voices Keita Suminoe (kiss×sis (TV)), Yusuke Takasaki (Green Green), Louis Asahina (Brothers Conflict), Oikawa (Major S2), Mario (Haven't You Heard? I'm Sakamoto), Deucem (KIBA), Guzman (KIBA), Lithuania (Hetalia World Series) and 3 more.
Keita Suminoe is voiced in Japanese by Ken Takeuchi.