Hong Ji Soo (Joshua) and Park Ji Yeon have been childhood friends. They made a promise to each other that when they grow up, they will both become an idol, then marry each other. But suddenly she left, to go aboard. Now she has come back to Korea, Joshua has become a famous idol, a top star. Ji Yeon tries the audition to become a trainee in his company. Coincidentally, Ji Yeon spilled her coffee by accident on the most famous idol in Korea and her company, Jeon Jung Kook. But soon, Jung Kook starts to feel weird about her, but Ji Yeon only has one thing to complete in her life. Her promise, but will he remember her?