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.

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.