In the long evolution, humans in the Moling World have evolved into three genders: Jiarou (female), Jiayang (male), and Xuan. There is no need to explain Jiaro and Kayang in detail, and Xuan is divided into Shuangxuan and Wuxuan. Shuangxuan is a bisexual body, while Wuxuan is a sexless body. Shuangxuan is both a boy and a girl, so neither of them has much influence. Wuxuan is different from Shuangxuan. Although she looks like Kayang, she has no gender distinction. Therefore, she can only be distinguished by Wuxuan's unique birthmark. The birthmark is a light blue birthmark of various shapes. Moreover, Wuxuan can only impregnate or impregnate one person in her life. If she has sex with others, her body will gradually weaken and die. , Therefore, Wuxuan is also a symbol of love. Regardless of whether she is willing or not, she will only stay with the person she has a relationship with for the first time. Because of this special characteristic, the sale of Wuxuan is repeatedly banned, so families who have Wuxuan in their family will hide it from the outside until the child grows up and finds his or her own partner. But even so, there are still cases of selling Wuxuan.