O Grande Sedutor

Soo Ji, Si Hyun, and Se Joo are best friends who have just graduated from high school. Like their crazy personalities, they do not graduate like normal students. They disclose an affair one of the teachers have been having by airing the footages on a big screen during the graduation ceremony. Meanwhile, Soo Ji’s first love, Lee Ki Young, tells her some hurtful words.

After the graduation, Si Hyun and Se Joo decides to go clubbing while Soo Ji is out with Ki Young. At the club, Si Hyun meets a woman and shares a kiss with her. It is later revealed that Si Hyun has kissed his fellow classmate’s mom. Meanwhile, Soo Ji decides to take revenge on Ki Young and targets Park Hye Jeong and Eun Tae Hee.

Soo Ji's mother and Si Hyun's father make an official announcement about their engagement. Only then, do Soo Ji, Si Hyun, and Se Joo find out about the adults' relationship. Ki Young, Soo Ji's first love, makes snide remarks about the surprise announcement, and Se Joo stands up for her. Meanwhile, the three musketeers try to find a way to stop their parents from getting married.

In order to prove Si Hyun's sincerity towards her, Soo Ji tells him to participate in a game of seduction. Si Hyun agrees to do so without hesitation. Si Hyun tries his best to make Tae Hee like him, but Tae Hee won't budge. Meanwhile, Soo Ji visits her mother's office and pleads her not to get married.

Si Hyun, Soo Ji, and Se Joo discuss how Si Hyun will seduce Tae Hee. Si Hyun tries to make Tae Hee feel like it is fate by purposely running into her often. In addition, he also tries to win Tae Hee's sympathy. However, Tae Hee does not easily waver. Finally, he gets the chance to eat with her, and they seem to bond. At that moment, Tae Hee tells him she does not want to see his face anymore.

Unintentionally, Si Hyun helps Tae Hee out at a nursing home. Tae Hee sees a soft and generous side to him that she never knew about, and her heart sof-tens. On their way back home, she tells him that she will not date him, and Si Hyun asks if she dislikes him that much. Meanwhile, Si Hyun feels a strange emotion toward Tae Hee.

Si Hyun and Tae Hee begin to bond, and Si Hyun tells her that he is afraid of hurting her. Tae Hee begins to have strange feelings toward him. Meanwhile, Soo Ji accidentally breaks a dish that Si Hyun received from the nursing home. Si Hyun gets very upset at her, and Soo Ji is shocked to see him react that way.

Si Hyun tells Soo Ji that he will stop chasing after Tae Hee. Upon hearing this, Soo Ji is frustrated. Meanwhile, Kwon Seok Woo meets Seol Young Won, Tae Hee's mother. They talk about the past and catch up. Amidst all this, Seok Woo's fiancee and Soo Ji's mother, Myung Mi Ri, is suspicious about him.