Oni was an orphan who grew up protecting Cassandra. After he lit their orphanage on fire, they escaped to the streets. They made due with Oni's street fighting wins. However, once he got badly hurt in a match, she seeks Elias' help. The two orphans temporarily stay in his care. Although he wanted the best for Cassandra, Oni kept up his brawling days, leading Elias to believe that he was possessed by a demon. When Elias caught Oni attempting to assault Cassandra in her sleep, he was banished back to the streets. She follows him later without knowing what happened.
One day, they hear news of the "Black Dragon", a man that supposedly possesses knowledge about everything. She wants to look for him to help solve the mystery behind their past, unsure if they are really related as Oni had originally claimed. In their ending, she shields Oni from one of Johann's blows, which angers him enough to finish the villain off. He carries her away from the island, promising to one day find the truth behind their powers.
Violent and resilient, Oni is a born fighter and antagonizer. Although he bullies his sister, he's actually very protective of her and sees her as his lone treasure in the world.
- Fire Attacks - Oni can fuel his attacks with fiery energy.
- Electric Attacks - Oni can fuel his attacks with static energy.
He is a power character that relies on his claw attacks to win. He is meant to be played with offensive strategies.
- Violent Death - Rage of the Dragons