In order to save her seriously ill mother, Wen Zhiyu takes her stepsister's place to enter into a marriage of convenience with Pei Yan when the stepsister is unable to fulfill the agreement due to circumstances. Believing it to be merely a mutual support pact, Wen Zhiyu faces life's twists and turns and misunderstandings, while the cold and steady Pei Yan extends a helping hand to her time and time again. Is it the responsibility of keeping an agreement, or a quietly budding heartbeat? Amidst day-to-day companionship, the two gradually find the answer, and also harvest sincere affection and personal growth.