Jung Soojung, Krystal, a high school student in senior year is meeting a big crisis in her life for faking her identity from a high school student to a high school teacher. Teaching high school senior class is already a hard task, but what even harder is to hide her identity from everyone, especially a group of the hottest, smartest, baddest boys, called EXO. Will she be able to keep her secret safe until the end of semester? Or will her true identity will be discovered?

Kim Jongin, Kai, the most popular boy in school who is a known for his handsomeness, intelligence and wealth. Being a student president doesn't mean he will obey every school rules, instead the title just gives him power to do thing the complete opposite. Yet, he still manages to keep his image as a hard-working, and outstanding student in front of the teachers and school principal. Will he be sharp-witted enough to notice the odds about his new teacher? Will Kai found out about Krystal secret?