The Ox King Gyumaoh broke taboo by eating human flesh and was sealed away.

Five hundred years later, humans and Youkai (demons) lived peacefully side by side in Shangri-La until a phenomenon known as the Minus Wave - a result of forbidden magic from an attempt to resurrect Gyumaoh - swept across the land. The Minus Wave turned Youkai into bloodthirsty monsters, driving them insane and causing them to turn on the humans with whom they had been living in harmony.

Four companions were charged with travelling to the West to discover the origin of the Minus Wave and find out who was responsible for trying to re-awaken Gyumaoh. The group was led by Genjyo Sanzo, an 'unconventional' priest. He was acompanied by Son Goku, the child-like Monkey King; Sha Gojyo, the lecherous half-kappa (water demon); and Cho Hakkai, a mysterious young man who fights using Chi energy.