Once upon a time, Togenkyo was a peaceful place where humans and yokai coexisted. However, men appeared who attempted to resurrect Gyumaoh, the Great Yokai who was slain by the war god Nataku Taishi and buried in Houtou Castle 500 years ago, by using a forbidden combination of chemistry and magic. The negative energy waves created by this caused the yokai to go insane and attack humanity. Kanzeon bosatsu sends Son Goku, Genjyo Sazno, Sha Gojyo, and Cho Hakkai west to defend the country. The four set out on a trip to put an end to the experiment to resurrect Gyumaoh. On the journey, they meet Hazel Grouse, who practices odd sorcery that uses yokai spirits to resurrect the dead, and his companions.