Joo Seung-gi and Yoo Ah-rin desperately have sex several times a day to have children, but they were not pregnant, so they were tested, and the result of the test was Seung-gi's infertility. After much consideration, Seung-gi asks his fiery friend Yoon-woo to have a relationship with Ah-rin, and after persistent persuasion, Ah-rin and Yoon-woo have a relationship. Afterwards, Seung-gi began to doubt the relationship between Yoon-woo and Ah-rin....