Thousands of years ago, when Yao Jun was still a little monster, he met someone who wanted to become his disciple. Yao Jun slapped his thigh and agreed.
He never expected his new disciple to be ungrateful. Yao Jun gave him everything, but the kid went crazy for some reason and desperately tried to sever their ties. Yao Jun was furious.
Wiping away his tears, he let the boy go.
A thousand years later, Yao Jun had become an old monster and took on another disciple. This one was a bit of an idiot, but was easy to look after, and Yao Jun was pleased.
Just as he was getting ready to retire, his eldest disciple appeared from nowhere and tearfully explained why he had acted that way.
Yao Jun refused him three times in a row.
Li Sheng: Master, I was wrong. Master!
Yao Jun: Too late. I won't be satisfied until I smash your head in.
Theme: After the founding of the country, monsters aren't allowed to reveal their true forms, but demons can.