Ha Yeong, shaped by a life of constant moving, keeps people at a distance until she unexpectedly opens her heart to Hui Won. When they attend the same school, the two create an Eternal List, a promise of things to do together as adults. After Hui Won breaks that promise, Ha Yeong's time comes to a halt, and she retreats to a cafe attic, cut off from the world. One day, Do Un appears holding the long-lost list, and with his arrival, Ha Yeong's frozen time begins to move again. Can a promise from the past lead them back to the present?