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
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.