High school students Han Tae-joo and Kang-gook have always been together for 15 years. Although they are friends, Gook is actually a bodyguard for Tae-joo, the heir of a chaebol family. But before they know it, they feel different kinds of feelings for each other. What does Gook mean to Tae-joo, and what does Tae-joo mean to Gook?