oo-mi, a quiet church lady, hates to stand out and always wears a cross necklace around her neck. She is a purist who has never met or dated any man. A bully, Won-joon, appears in front of her. Hearing that Joo-mi is still chaste, the desire to seduce her intensifies. For Won-joon who meets women once a month, it was easy to seduce Joo-mi, but it was not easy to steal her virginity. Won-joon, who said goodbye to Joo-mi, who would never let him have sex, started dating Na-yeong. They brag about it to Joo-mi and insult her. Jooo-mi, who was insulted by Won-joon, who she loves so much, had sparks in her heart. Joo-mi decides to have sex with her church friend in revenge against Won-joon.