Joo Yeon-ho, a private academy instructor, finds his former student, Ahn Ji-hye, whom he met during tutoring four years ago, back completely transformed! Forced into an emotionally draining cohabitation due to circumstances… The diligent and intelligent Ji-hye is nowhere to be seen, replaced by a childish brat! Will the immature Ji-hye be able to grow into a ‘cool adult’?