Unkai Saitou

He appears with both of his eyes red and has the ability to see ghosts the same as Yakumo. He is actually a cruel and twisted person. He sees everyone's true nature as darkness. He is Yakumo's biological father and a spirit of the dead. His one target is to take over Yakumo's body once the boy is completely drown in hatred. He planned to kill both Yakumo's uncle and his guardian Gouto. Yakumo was stronger than he appeared and both souls couldn't align together.