After falling in love with Yang Kang, Mu Nianci would later conceive a child with him. Her son, Yang Guo, would be the main protagonist in The Return of the Condor Heroes, the sequel of The Legend of the Condor Heroes and become one of the new Five Greats at the end of The Return of the Condor Heroes.
Mu Nianci died somewhere between the end of The Legend of the Condor Heroes and the beginning of The Return of the Condor Heroes, leaving her son Yang Guo an orphan until Guo Jing and Huang Rong came upon him several years later and took him back to Peach Blossom Dock
Mu Nianci’s parents were poor farmers. Suddenly one day they found a injured Yang Tiexin. They took care of him and helped him recover. Soon Yang Tiexin left for a while. A few months later Mu Nianci’s parents were killed. When Yang Tiexin returned to visit them he saw them dead and a toddler Mu Nianci. He adopted her and changed his name to Mu Yi. They would travel everywhere because everyone thought Yang Tiexin was a Kung Fu performer but actually they travelled to find his long lost wife, Bao Xiruo.
Yang Tiexin held many betrothal competitions for Mu Nianci in the hopes of one day meeting Bao Xiruo. Eventually, they meet Yang Kang who helped them defeat 2 challengers. Yang Kang then fought Nianci for her hand in marriage and defeated her, but took her shoe and refused to marry her, breaking the rules of the betrothal contest.
Nianci and her foster father were eventually captured by Yang Kang as the prince thought they were lowly Song men. Yang Kang tricks Mu Nianci into believed that Yang Kang was going to marry her but he doesn't manage to fool Tiexin. They are eventually released by the princess, actually Bao Xiruo. The three then try to escape
However, during there escape, they are chased by Wanyan Honglie's men, including some wulin martial artists such as Sha Tongtian and Ouyang Ke. Ma Yu and Qiu Chuji arrive and hold these men off but the three are forced back by soldiers and are eventually trapped by Wanyan Honglie's men while Qiu Chuji, Ma Yu and Wang Chuyi, who was summoned by the other taoists continued fighting Wanyan Honglie's associates. Mu Nianci tried to help but her kungfu was far inferior to the others and Yang Tiexin and Bao Xiruo eventually committed suicide after getting cornered and outnumbered by Wnyan Honglie.
Mu Nianci was described to be a beautiful, elegant, and graceful young girl.
When she was 13, Mu Nianci learned the "Carefree Fist" (逍遙遊) from Hong Qigong for three days in a ruined temple in Xinyang. Using the early martial arts training by her foster father as a foundation, she masters the skill within three days. When a combatant utilises the skill, he or she is elegant, extremely light, agile, and appears as if he or she is dancing. Every motion is as beautiful as that of a jade yanornis or huge eagle.