Ji Sharen believed that only Yan Fenghuang could make Long Ao Zhen happy. That girl was also the only girl he believed since she was their childhood friend.
This also what made Yan Fenghuang was so full of herself. She got Ji Sharen backing and the people hope thus leading her to think that it was only natural for her to become the future empress.
Time passes by and Ji Sharen yandere characteristics become even worse than before. It even rubbed on Long Ao Zhen making the man more possessive than most dragons until one day the poor little prince awakened his second nature.
A yandere.
Long Ao Zhen killed a servant become that servant touched his favourite pet. This incident made the emperor and the previous emperor realized there's something wrong with the crown prince.
Everyone was terrified of Long Ao Zhen and only Ji Sharen wasn't.