The 16-episode arc unfolds across key narrative shifts:
Beginning (Ep 1–4): Four years after high schooler Saet-byul kissed Dae-hyun when he bought her mints instead of cigarettes, Dae-hyun hires her as a night-shift part-timer at his struggling store. Initial suspicions of theft and gang activity are disproved when he discovers she actively protects the shop.
Middle (Ep 5–10): Friction mounts as Dae-hyun's wealthy girlfriend Yeon-joo displays jealousy. When Yeon-joo's mother hires and humiliates Dae-hyun's mother as a house cleaner, Dae-hyun recognizes the insurmountable class barrier and breaks up with Yeon-joo. Saet-byul confesses her long-held love at the beach.
Climax (Ep 11–14): Saet-byul protects her sister Eun-byul from an idol debut blackmail scandal. After Dae-hyun becomes a corporate HQ consultant and sees Saet-byul study tirelessly for her GED, he presents her with red tulips and confesses his love.
Finale Twists (Ep 15–16): Guilt over potential friction between Dae-hyun and corporate HQ leads Saet-byul to secretly leave for a rural flower nursery. Dae-hyun resigns from HQ, tracks her down, and convinces her to return. Saet-byul passes her GED, returns as full store manager, and joins Dae-hyun in a warm romantic conclusion.