Number One: Eighteen-year-old Ha-min suddenly begins to see the number "365" every time he eats his mother's homemade meal—and the number drops with each bite. Believing it to be a countdown to his mother's death, he distances himself from her and her cooking. Years later, still haunted by the number, Ha-min lives cautiously, preparing for the worst. Just as he begins to find peace with his girlfriend Ryeo-eun, an unexpected truth turns his world upside down.