To save her ailing mother, the country girl Yoon Eun-seo goes to Seoul, but unexpectedly saves the powerful chaebol Kang Ji-ho on the train. She didn't know she had already been betrayed by her best friend. On her wedding day, betrayed by her childhood friend, she was given to a wealthy tycoon by her father. In a desperate situation, Kang Ji-ho saved her. He pressured her step by step, and she fled in a hurry, only to find that the boy who had saved her in her childhood overlapped with this man before her eyes. This was a promise she had already forgotten, and a deep obsession he had held for over a decade.