The Taeyang Group is the most powerful conglomerate in South Korea, but it is rumored to be under a century-old curse: the first bride of the eldest son will always die. When the cold-hearted heir Choi Kang-joo is set to marry the spoiled heiress Jang Yi-kyung, she suddenly disappears, leaving the family in a panic to maintain their corporate alliance. They recruit Na Doo-rim, a kind-hearted girl from a small fishing village who looks exactly like the missing heiress, to pose as the bride-to-be. As Doo-rim navigates the high-stakes world of the Taeyang family, she finds herself falling for Kang-joo, who begins to soften under her genuine warmth. However, the mystery surrounding the curse deepens as supernatural elements and dark family secrets come to light. Doo-rim must fight to break the cycle of tragedy while protecting her heart from the very man she was hired to deceive, all while the true heiress plots her return.