
Quick answer — Kouichi Nagano voices Ryokan Kurita in Eyeshield 21, Helmeppo in One Piece Film: Red, Maccus in One Piece Special: Open Upon the Great Sea! A Father's Huge, HUGE Dream! and 4 more characters.
Kouichi Nagano voices Ryokan Kurita (Eyeshield 21), Helmeppo (One Piece Film: Red), Maccus (One Piece Special: Open Upon the Great Sea! A Father's Huge, HUGE Dream!), Rai Chou (Beyblade), Kosuke Nakajima (Gantz), Masashi Yamada (Gantz), Yoshiki Satou (Tenjho Tenge).
Ryokan Kurita is voiced in Japanese by Kouichi Nagano.