After ten years of marriage, Chen Jianji and Lin Qingxue seemed fulfilled yet cold and alienated. After Lin Qingxue fell into an accidental coma, Chen Jianji opened the diary she guarded desperately, only to realize his many years of deep affection were merely a used human favor debt, and she had someone else on her mind. In the midst of collapse, he returned to his third year of high school, determined to no longer entangle with Lin Qingxue, make up for family affection, and prepare for the college entrance examination. However, due to the mysterious diary simultaneously exposing the truth, he was forced to face misunderstandings, indebtedness, and shifting feelings.