Office worker Truly Lin is stuck in a lonely, corporate routine when a cassette recording of an old song sends her spiraling back to her teenage years. At 17, she was a quiet, unremarkable high-school girl who secretly adored the school's hottest guy, Ouyang Fei-Fan. Meanwhile, the school's notorious gang leader, Hsu Tai-Yu, is infatuated with the popular girl Tao Min-Min. Through a strange twist of fate, Truly and Tai-Yu form an unlikely alliance — entering a "Dumped & Lonely" club whose mission is to break up couples so they can each chase their first love. Their hijinks, treks through cassette-tape nostalgia and floppy-disk exchanges, and the bittersweet awakenings of youth unfold into a journey of first love, self-discovery and the enduring power of memories.