Kyoto, Mankihara Sinkaiin.
It was built by the gods in ancient times with the original intention of suppressing the four evil spirits. Later, it gradually became a place to suppress evil.
Today, the four evils have long since disappeared, and the gods realize that they are boring, so they have a duel every ten years. The winner can erase his original sin, and the family is freed.
Now, it is 2017. To this day, only seven people are left: Bai Ze, Bi Fangniao, Taotie, Chaos, Xuanwu, Phoenix, Jiaolong and their descendants, competing for hegemony.