Xi Yan, who had obtained the "Yao" technique, was gentle and close to nature. His master gave him the task of assisting his junior brother in practicing the "Xiao" technique.
Leng Xiaoyi, who has obtained the "Xiao" technique, must become a king and have the character of a king before he can practice the "Xiao" technique.
By the way: Actually Xi Yan's master is a rotten girl