An erotic sister-in-law and fake brother-in-law get horny! You only live once. Jeong-min lives everyday in gambling debt and sex. He finds out his rich twin brother is missing and plans to take his place but his plans get complicated when his brother's sister-in-law Sae-eun appears. Jeong-min and Sae-eun who loves him start living together. Will Jeong-min overcome Sae-eun's seduction and put his brother's wealth in his hands?