When Jiu Seo moves out of her childhood friend's mansion and into a small one-bedroom apartment, she thinks her world is ending -- that is, until she meets Hajun and Hayul, the neglected children who live downstairs. When a scouting offer comes in for Hajun to join an idol survival program, Jiu encourages him to audition, completely unaware of how it will change the trajectory of her and everyone else's lives forever.