Good Day To Have Sex: An ordinary office worker, Jeong-min, successfully marries Yuri, whom he had liked in college, and is living an ordinary but happy married life. One day, his older brother Jeong-tae, whom he has not contacted for 10 years, appears, and he decides to live with him for a while at his mother's earnest request. However, he does not know that his wife Yuri's first love was his own older brother Jeong-tae. His older brother Jeong-tae is surprised to learn that his younger brother's wife is Yuri. Yuri is also surprised to meet Jeong-tae, but on the other hand, his heart flutters...