Kaka, an unusually strong girl with a talent for combat, sees it has her duty to protect and assist her caretaker and master Genjou-sama, a kind but frail young priest who nearly died saving her from a tiger. When poisoned water threatens to destroy their village, Genjou-sama 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-sama, 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-sama back, relinquishing the priest's body and retrieving his soul from the underworld. Will Kaka take the risk?