Chan lives every day like it is summer vacation. Haran is trapped in a lonely winter. When their forgotten past reunites them, Chan is determined to gift her another spring. Through laughter and tears, they face winter together and reach their spring in this heartwarming romance.

Ace NIS agent Jung Hae-seong is demoted after a mission failure. He goes undercover at a high school to locate King Gojong's missing gold, meeting his teacher Oh Soo-ah, who sees him as her lost first love, stirring old heartbreak.

In Joseon, a vengeful crown prince and a memory-lost merchant mysteriously swap bodies, unraveling a web of chaos, secrets, and unexpected fate.