Gensou Maden Saiyuuki

A long time ago, humans and demons coexisted peacefully. This changed when demons turned violent and sought to free Gyumao, a malevolent demon sealed away for millennia. A former priest named Genjo Sanzo joins forces with three demons—Sha Gojyo, Son Goku, and Cho Hakkai—and sets out on a dangerous journey to the west. Their mission is to prevent the demons' plan to revive Gyumao and to reestablish balance between humans and demons.