Kaka, an unusually strong girl with a talent for combat, sees it has her duty to protect and assist her caretaker and master Genjou, a kind but frail young priest who nearly died saving her from a tiger. When poisoned water threatens to destroy their village, Genjou leaves for the capital to find a solution. In his absence, demons burn down their formerly peaceful village and transform the villagers placed under Kaka's care into monkeys.

Kaka flees in a desperate attempt to find Genjou, only to find a haughty powerful spirit is now using his body as a vessel! She learns that the human Emperor has been secretly replaced by the evil Demon King, and that this spirit has come back for one simple purpose: to restore order. The contact he offers is simple. If she accompanies him on his journey to the capital and all goes according to plan, the spirit will give Genjou back, relinquishing the priest's body and retrieving his soul from the underworld. Will Kaka take the risk?