Ga-ran and Nam-joon used to be classmates in elementary school. Ga-ran, a tomboy, that prefers trousers to skirts and loves to perform taekwondo rather than to play piano. Nam-joon on the other hand is a Mr. Perfect, who cares all about looking good, having a fine brain and to be popular in school, especially among the girls. One day, Ga-ran sees Nam-joon giving away sweet bun, which Ga-ran's friend gave him, to another girl. Ga-ran beats Nam-joon up and their rivalry lasts throughout the entire high school period. A few years after college, Ga-ran and Nam-joon meet again as adults, both recovering from recent break-ups. Despite their constant bickering, they gradually realize that they're meant to be.