Twenty years ago, Takeda Kuni-sensei secretly saw his father giving a scroll to his junior apprentice Gang-zheng. Kuni-sensei believed that the scroll contained "martial arts secrets". Later, Gang-zheng was expelled from the school and cut off all ties with the karate community. One day, a new immigrant named Xiao-yue was bullied, and the prospective Olympic karate athlete Zhuang Hui took action. The gangster Zhi-hao who was dragged into the fight was involved. Gang-zheng passed by and stopped the fight, but he didn't expect that everyone went to the police station...