Weiyangsheng (未央生) is an egoistic young scholar who often boasts of his aspiration to marry the most beautiful woman in the world. He seeks neither fame nor glory, and prefers to indulge in women and sex. A monk called "Budai Heshang" (布袋和尚; lit. "Monk with a Cloth Sack") once urged him to give up on his philandering ways and follow the path of Buddhism, while his father-in-law, Taoist Tiefei (鐵扉道人), also attempted to persuade him to be more decent, but Weiyangsheng ignored both of them.

On a trip to the capital city, Weiyangsheng encounters Saikunlun (賽崑崙), a bandit, and becomes sworn brothers with him. Saikunlun introduces Weiyangsheng to Tianji Zhenren (天際真人), a Taoist magician, who surgically enhances Weiyangsheng's penis by splicing strips of a dog's penis into it, causing it to be enlarged and become more 'powerful'. With Saikunlun's help, Weiyangsheng gets involved in illicit sexual relationships with many married women, including: Yanfang (艷芳), the wife of Quan Laoshi (權老實); Xiangyun (香雲), the wife of Xuanyuanzi (軒軒子); Ruizhu (瑞珠), the wife of Woyunsheng (臥雲生); Ruiyu (瑞玉), the wife of Yiyunsheng (倚雲生).

When Quan Laoshi learns of his wife's relationship with Weiyangsheng, he is furious and is determined to take revenge. He disguises himself and infiltrates Weiyangsheng's household, where he has an affair with Weiyangsheng's wife, Yuxiang (玉香), and makes her pregnant. Quan elopes with Yuxiang and sells her to a brothel to be a prostitute. Later, he realises that he has committed grave sins and decides to show penitence by becoming a monk and studying under Budai Heshang.

Meanwhile, in the brothel, Yuxiang is trained in a special technique – writing calligraphy by clutching a brush with her genitals. Later, she meets Xuanyuanzi, Woyunsheng and Yiyunsheng, and has sex with each of them. When Weiyangsheng visits the brothel, Yuxiang recognises her husband and commits suicide in shame. Weiyangsheng is given a good beating, which makes him come to his senses. He decides to follow in Quan Laoshi's footsteps and become a monk under Budai Heshang. He also castrates himself to avoid being distracted from this calling by his surgically enhanced penis.