Quick answer — Tetsuo Mizutori voices Kuzuu in Future Boy Conan, Luca in Future Boy Conan, Oiton in Future Boy Conan.
Tetsuo Mizutori voices Kuzuu (Future Boy Conan), Luca (Future Boy Conan), Oiton (Future Boy Conan).
Kuzuu is voiced in Japanese by Tetsuo Mizutori.
