Dahyun and Sana used to play together as children. Sana was 6 and Dahyun was 5, but one day Sana's family had to move back to Japan. The pair make a silly promise to go to the same university one day--NYU. The campus surrounded the park where the two would meet to play. 15 years later, Dahyun remembers the promise, but not the person. Sana hardly remembers her old life but she has a charm from those early days. Will life bring them back together?