Ho Goo Hee (Kim Hyang Gi) is a quiet, sweet girl who is constantly bullied by the other students, partly because her name sounds like the word “fool.” Ji Hoon (Park Solomon) is a brooding, popular boy who reluctantly comes to her rescue more times than he would like. The only positive thing in Goo Hee’s life is her close family friendship to Cha Eun Woo (Cha Eun Woo), a popular K-pop idol, who treats her like a younger sister. Things start to take a strange turn in Goo Hee’s life when an app on Goo Hee’s phone called Revenge Note pops up one day and asks her to write in the name of someone who is bullying her.