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.
In volume 6 of the light novel, it is revealed that he is, in fact, a ghost so he cannot cause physical harm to him. That is why he always manipulate others’ emotions to cause them to commit crimes rather than doing anything himself. Although it is uncertain, it is said that he had died two or three years ago. He wants Yakumo to fall into despair so that he can take over Yakumo’s body (likely due to Yakumo being the only child he fathered to inherit his red eyes and still be alive) because a soul can only take over a body if it is compatible, that is why he manipulated Sakakibara into murdering Isshin.
