[Youth on campus + Reunion after a long absence + Ten-year appointment] On the seventeen-year-old Dongxuetian, she called him "The Prelude to Winter" (Xu Dong), and he called him "The Remaining Summer" (Yu Xia). A transfer of schools made two people with very different personalities become roommates. In the midst of physics tutoring, hallway jokes, and taking care of a high fever, a subtle relationship quietly grew. However, the conversation that Xu Dong accidentally overheard convinced her that Yu Xia was good to her just because she looked like his childhood sweetheart who went abroad. With knots and misunderstandings, she left for England without his knowledge, leaving only the promise of "then forget me." Ten years later, when she returned to China as promised, what she waited for was a wedding invitation from him. In the letter, she wrote down her explanation and apology for being late, and at the end of the letter, he added a ten-year answer in trembling handwriting. This is a story about the coincidence of names, youthful misunderstandings, long waiting, and finally passing each other, taking place between winter and summer.