
Quick answer — Kouta Hirano worked on Hellsing Ultimate (Original Creator), DRIFTERS (Original Creator), DRIFTERS OVA (Original Creator) and 2 more anime.
Kouta Hirano worked on Hellsing Ultimate (Original Creator), DRIFTERS (Original Creator), DRIFTERS OVA (Original Creator), Hellsing (Original Creator), HELLSING: THE DAWN (Original Creator).