Li Chuntian (Choi Soo-young) is a nutritionist. She once underwent an extremely dangerous heart transplant surgery. Fortunately, the surgery was successful and Li Chuntian got a second life. Li Chuntian and her boyfriend and colleague Jiang Dongxu (Lee Jun-hyuk) have been dating for many years. The two have long decided that they want to enter the marriage palace hand in hand. One day, Li Chuntian met Jiang Dongxu's brother Jiang Donghe (Gan Woo-sung). What Li Chuntian didn't expect was that her heartbeat accelerated for unknown reasons. Not only that, when she saw Jiang Donghe's child, her heart was inexplicably filled with sadness and pain. Li Chuntian knew that all this was related to the heart that did not belong to her beating in her chest. Li Chuntian was completely unable to control herself and was deeply attracted to Jiang Donghe.