
Quick answer — Toshinobu Iida voices Mukuro Rokudo in REBORN!, Kozufutoro in HUNTER×HUNTER: Greed Island, Ryota in Baka and Test - Summon the Beasts.
Toshinobu Iida voices Mukuro Rokudo (REBORN!), Kozufutoro (HUNTER×HUNTER: Greed Island), Ryota (Baka and Test - Summon the Beasts).
Mukuro Rokudo is voiced in Japanese by Toshinobu Iida.