Gensoumaden Saiyuuki (2000)

Saiyuki

Many years ago, humans and demons lived in harmony. But that unity ended when demons started attacking humans and plotted a mission to unleash Gyumao—an evil demon imprisoned for thousands of years. Now, Genjo Sanzo, a rogue priest, must team up with three demons—Sha Gojyo, Son Goku, and Cho Hakkai—and embark on a perilous journey to the west to stop these demons from resurrecting Gyumao and restore the balance between humans and demons on Earth. (Source: ANN)