The story centres around a series of attacks on popular high school students or commonly called flower boys that occurred on the 14th of each month, which started on Valentine's Day. Some students; Kibum (played by Kim Ki-bum) and Donghae (played by Lee Dong-hae), decided to investigate the incidents and find the culprit, while some targeted students; Heechul (played by Kim Hee-chul) and Kangin (played by Kim Young-woon) try to bait the culprit into attacking them as to raise their popularity.