Smoking Behind the Supermarket with You follows Sasaki, a weary salaryman whose days are brightened by a single ritual: stopping at the neighborhood 24-hour supermarket to see Yamada, the cheerful cashier whose smile helps him forget his miserable job and his boss's constant scolding.
One night, however, Sasaki arrives after Yamada's shift has ended and is left searching for a place to smoke. Behind the store, he is called over by Tayama, a bold and teasing woman who quickly notices his habit of coming by for Yamada. Instead of turning him away, she draws him into her own offbeat company and even tells Yamada about his obvious interest, throwing Sasaki's routine into amusing chaos.
As Sasaki begins returning not only for Yamada but also to see whether Tayama is around, his late-night cigarette breaks slowly turn into an unlikely friendship. Beneath Tayama's mischievous attitude lies more than she first reveals, and the quiet supermarket corner becomes the unlikely stage for small comforts, shifting feelings, and a bond that grows one cigarette at a time.