Plot
Gong Hi-ji stands up for her friend who is excluded in the Charatting Single Party organized by Club Med. She cannot endure these injustices, such as the smoking high school students or company between young girls and middle-aged men in return for money. The moment she is about to begin attack, her dream boy appears. But he is the head of Club Med named Kim Hyeon-jun. Whether he is the enemy or not, she falls towards him, and starts to take action. She sneaks into the hotel room where he sleeps, and finally gains his diary. Hyeon-jun's schedule and hobbies, and all about him are valuable information for her. From this information, Hi-ji goes everywhere Hyeon-jun goes, at times softly and at times strongly. Although she is annoying, Hyeon-jun finds her cute. Before long, he finds out that it is all part of her plan and what is worse is that his fiance appears. Still, Hi-ji doesn't give up until the day she sings "Oh! Happy Day." She starts a project with friends, family, cousins and all the people she knows in order to achieve her goal.
