Zheng Wei enters college as a civil engineering major with a clear plan: stay in the same city as her childhood playmate, Lin Jing, and marry him someday. When Wei visits Lin Jing at his dorm, she learns that he has left for America, leaving her confused and heartbroken. Back in her own dorm, Wei grows close to three memorable roommates: Ruan Wan, Li Weijuan, and Zhu Xiaobei, each bringing a different dream and energy to their shared space. The four girls trade stories about life goals and cheer one another on, especially Ruan Wan’s ambition to keep a youthful spark alive no matter what the future holds.
Wei also befriends two architecture majors who will shape her college years: the disciplined, steady Lao Zhang and his roommate Xu Kaiyang. Kaiyang, from a wealthy background, pursues Wei romantically, but she treats him more as a friend than a partner. One evening, Wei goes to Lao Zhang and Kaiyang’s dorm to borrow a DVD. The room is cluttered and chaotic, except for one bed that is neat and clean—the bed of their roommate Chen Xiaozheng. Wei fiddles with a building model on the table, and Xiaozheng bursts in, shouting questions about what she is doing. In a tense moment, Wei knocks the model to the floor, sparking a clash between curiosity and defense.
Enraged, Wei demands an apology, but Xiaozheng remains calm, insisting that he has nothing to apologize for and blaming her for touching his model. From that confrontation, Wei resolves to humiliate and pesters him until she gets the apology she seeks. Yet as their cat-and-mouse game unfolds, Wei discovers something deeper: she is drawn to him. From conversations with Lao Zhang and Li Weijuan, she learns that Xiaozheng comes from a poor family and was raised by a strict mother, a background that helps explain his reserved, disciplined demeanor. Wei’s feelings grow, and she eventually agrees to date him.
Their relationship thrives even as their personalities clash. Wei’s exuberance and spontaneity often collide with Xiaozheng’s seriousness, and he bluntly asks why life must be so precise and orderly. He answers with a metaphor that sticks: “My life is like a building that can only be built once, so I cannot afford any margin of error, not even a centimeter of deviance.” This line crystallizes the tension between risk and meticulous preparation that threads through their romance.
Graduation draws near, and at the on-campus job fair Wei hopes they will land the same position. Unbeknownst to her, Xiaozheng has applied for and earned a graduate fellowship to study architecture in America. When Wei finally learns the truth, he explains that he could not tell her sooner because he did not want to hurt her and believed he needed to minimize any chance of error in his life.
A few years pass, and Wei has grown into a mature, successful professional. She unexpectedly encounters Lin Jing again, who confesses that his abrupt departure years earlier was tied to his father’s affair with Wei’s mother. He never went to America and instead avoided Wei. At the same time, Xiaozheng returns as an accomplished architect, yet he finds life hollow without the spontaneity they once shared. He regrets letting Wei go, and he longs to rekindle what they had.
Wei, though, meets Xiaozheng’s renewed gaze with firm resolve and initially rejects his attempt to rewrite their past. Tragedy strikes when Ruan Wan dies in a car accident while trying to meet her university boyfriend before she would marry someone else. Grief-shattered, Wei contemplates marriage to Lin Jing, only to be told of another girl who loved him during their separation, which leads her to withdraw from the idea.
Later, Wei and Xiaozheng cross paths again at the aquarium—one of their happiest havens from years past—and they share a quiet moment of nostalgia. Xiaozheng asks if they could start over and love one another again, but Wei’s response is tempered by memory: they spent their youth together, and they owe each other nothing. “Youth is something you can only relive in memory.” The encounter makes it clear that they cannot return to who they were, and rekindling their romance feels unlikely, even as the ache of what they shared remains.
