Shaka Nyorai was born in the human realm as a prince of the Indian Kshatriya clan named Siddhartha. However, he abandoned his home, attained enlightenment and became a Nyorai. In Japan, several followers refer to him affectionately as "oshaka-sama." In order to defend humanity, he fights vices as the leader of the Buddhas.

(Source: Namu Amida Butsu! Wiki)