Outdated Hong Kong boxing champion Cheng Hui (played by Zhang Jiahui), who has not fallen behind in boxing, is addicted to gambling and heavily in debt, in order to avoid debt collectors. In the shared house, Cheng Hui met a mother and daughter. The mother (played by Mei Ting) suffered from mental illness. The little girl (played by Li Xinqiao) not only had to go to school but also took care of her mother. Cheng Hui and the little girl hit it off very well. The two often dressed up as small animals and rehearsed sketches to amuse the little girl's mother. At the same time, the rich second generation Lin Siqi (played by Peng Yuyan) suffered a family accident. His father (played by Gao Jie) failed in business, lost everything, and spent all day in bars. In order to encourage his downhearted father to start life again, Lin Siqi signed up for MMA. To this end, he signed up for a boxing club, where he met Cheng Hui who was working in the club, and worshiped him as a teacher to learn boxing. After several months of study, Lin Siqi won several consecutive MMA fights and became the new boxing champion. Immediately, he was challenged by another master (played by An Zhijie), and Lin Siqi was injured and retired. At the same time, the debt collector found Cheng Hui and accidentally injured Mei Ting's mother and daughter during the fight. For this reason, Cheng Hui felt deeply guilty and didn't want to hurt others, so he began to retrain his mixed martial arts skills, hoping to win the MMA competition and get bonuses to repay his gambling debts. In MMA, Cheng Hui challenged boxing in his forties and was not favored by others. And the opponent he encountered was none other than An Zhijie, the new boxing champion who defeated his apprentice Lin Siqi..