Their surname contains the four directions of southeast, northwest and northwest, just like their family name is Sifang.
They are not ordinary humans, they are four legendary races related to moonlight.
Dong Wang is a human-wolf family.
Simon is from a mermaid family.
Nangong is a vampire family.
Hojo is a ghost family.
All four races are more or less affected by moonlight. Their future is controlled by their birthstones, and they obey the orders of their ancestral family, a family called the Gods - Xuanyuan. Taken from the surname of the ancient Yellow Emperor.