Once an all-boys school, expect for Kwon Yuri, SM High, a renowned school full of reckless students, has recently become a co-ed school. However, with the female population still remaining a minority even after the change over the recent years, Im Yoona takes it into her own hands to reform the school and allow a chance for the girls to feel safer in the rough environment.

Even the teachers are on her side. Training, studying and even becoming the first female student council president of the school, Yoona has gained a reputation, among the male students body as an uptight boy-hating demon dictator and as a shining hope for the teachers and fellow female students.

However, despite her tough-as-nails appearance, she secretly works part-time at a maid café in order to support her family because of her father who fled when he couldn't pay his debt. Which led her to her hatred for men.

Unfortunately, Yoona's secret is soon discovered by Kwon Yuri, a popular tom-boy at SM High. Instead of exposing it to the school, though, Yuri keeps it for herself and even becomes a regular at the café, much to Yoona's chagrin.

Known for being a genius in pretty much everything from academics to athletics and for having rejected numerous confession of her female peers, Yuri takes a liking to Yoona due to her standing out from other girls who are attracted to her because of her looks.