Yalkae, a Joker in High School

Na Du Su, who sports the nickname of "Yalkae" (meaning "cheeky, cocky person" ), has been in the second year in high school for two years. His partner-in-mischief, Yong Ho, whose father runs a hospital, is also repeating his grade. Together, they play pranks on their friends and teachers and neglect their studies, thereby earning a notorious reputation as "problem" students. One day, Du Su goes to the house of a teacher named Baek Sang Do, who rents a room from a grocery store owner, for after-school lessons. There, he falls for In Suk, whose mother owns the grocery store. When a classmate named Ho Cheol tells on him to Mr. Baek, he decides to get Ho Cheol back. During class, he paints Ho Cheol's glasses red and yells, "Fire!" Ho Cheol ends up getting his glasses broken, and Du Su gets sent to the principal's office.