Young-joo, who is focused on adjusting to her new job, grows tired of the constant complaints of her boyfriend, Jae-yoon, who's serving in the anti-aircraft unit at 77 A Tower. She breaks up with Jae-yoon, and he accepts the breakup with a heartfelt voice message. Upon hearing this, Young-joo heads to the tower to meet Jae-yoon, but on her way there, she encounters an unexpected incident.