He is a noble and rightful leader of a pack in the Musashi Province.
He is black and white.
His ancestors and ancestors of the neighbor pack fought constantly until he stopped the war and offered peace. He once rescued the puppies (one of them being Zack) of neighbor pack's leader from human and drowning. This made the other leader accept his offer of peace.
Later, he heard news of monster bear Akakabuto and as a rightful male, Reiji joined Ōu with his soldiers to help them to defeat the bear. He left his territory for his three sons to control. Unfortunately, Reiji and his minions died in the battle against Akakabuto which caused new conflicts on his home area.
- Some fans believe Reiji Hidaka is of the breed Siberian Husky, but nothing is confirmed.