Jong-In and Kyungsoo were childhood friends and Jongin's promise was to always stay by and protect Kyungsoo, no matter what. One day, Jongin's family, after facing bankcrupcy, decides to flee the country and move to Japan. Without having a chance to explain to Kyungsoo, Jongin never returns to school making him think that he was abandoned. After 7 years, Jongin returns to Korea as Kai (his Japanese name) and fate brings him together with Kyungsoo once again. Only this time, they both don't recognize each other.