Graduation Trip: Summer vacation of the last year of high school, Yu-na and He-yoon go to Incheon, deceiving their parents to go to a rock festival. However, the concert which they want to see is postponed until the following day. They have no choice but to book tickets for tomorrow and decide to spend one more day in Incheon. The next day, the tickets that Yu-na definitely held in her hand the previous day disappear. He-yoon contacts her cousin to borrow money…