Ouma, the Spirit of Vengeance, is the final ghost fought in the series. He appears in Episode 20, returning to take revenge on Satsuki and her family for his multiple instances of imprisonment in the past.
Ouma is a massive, imposing monstrous humanoid, with skin and claws made of rock. His head and ugly features appear like roughly carved, faceted stone. He has bright blue eyes with slit-like pupils and jagged, sharp yellow teeth. He has huge, stony forearms and a a spiked Ankylosaur-like tail.
Supernatural Abilities Edit
Ouma has powers over stone and earth elements, able to create enormous splits in the Earth's crust that expose lava. It is also explained in the Ghost Diary that Ouma's revival also awakens every other ghost that had been put to sleep controlled under his power. Ouma also has the ability to possess and control scores of humans as Satsuki's class and teacher come under his power, luring Satsuki and Keiichirou into the Old School. In these ways it is arguable that Ouma is among the most powerful ghosts that Satsuki faces.