
Quick answer — Hiroya Oku worked on INUYASHIKI LAST HERO (Original Creator), GANTZ:O (Original Creator), Gantz: Second Stage (Original Creator) and 1 more anime.
Hiroya Oku worked on INUYASHIKI LAST HERO (Original Creator), GANTZ:O (Original Creator), Gantz: Second Stage (Original Creator), Gantz (Original Creator).