Zheng Wei started her college freshman year as a civil engineer major to be in the same city as her childhood playmate, Lin Jing, whom she determined to marry one day. When Wei visited Jing at his college dormitory however, Jing’s roommate told her Jing left for America. Unable to understand why Jing abruptly left without saying goodbye, Wei was left confused and heartbroken. Back in her college dormitory, Wei became close friends with her three roommates, Ruan Guan, the most beautiful and popular girl in the class; Li Weijuan, a practical and realistic girl who comes from a poor town but determined to marry well; and Zhu Xiaobei, a tomboy. The four girls talked about their goals in life, and all cheered to Ruan Guan’s ambition—to have a youth that never fades away.
Wei was befriended by architecture majors Lao Zhang and his roommate Xu Kaiyang. Kaiyang came from a well-to-do family and started a romantic pursuit for Wei, but Wei only regarded him as a friend. One evening Wei went to Lao Zhang and Kaiyang’s dorm room to borrow their DVDs. Wei was amazed and disgusted by the messy condition of the male dorm room, except one bed and corner that is uncannily neat and clean. Lao Zhang explained that this bed belonged to their disciplined and hardworking roommate, Chen Xiaozheng. Laozhang went out of the room to find his DVDs, leaving Wei alone in the room. Wei saw a near-finished building model on the table and curiously started to fumble with the parts. At this moment Xiaozheng came back and angrily yelled out, “What are you doing?” Startled and swinging around to see who yelled, Wei knocked the model off the table. Xiaozheng managed to save his model by shoving Wei out of the way, who fell in a mess on the floor.
Enraged in humiliation, Wei angrily demanded an apology from Xiaozheng, but Xiaozheng coolly replied that he has nothing to apologize for and that it was her fault for touching his model. From this moment, Wei was determined to repeatedly humiliate and pester Xiaozheng until she gets the apology she believed she deserves. Through her attempts Wei came to the startling realization that in fact, she liked Xiaozheng. From Lao Zhang and Weijuan, Wei learned that Xiaozheng comes from a poor family and was raised by a strict mother, hence his aloof and disciplined personality. Wei declared her interest in Xiaozheng, then openly, relentlessly, and shamelessly stalks Xiaozheng to get his attention, much to his annoyance. Eventually, Xiaozheng, impressed by her enthusiasm, determination, and spirit, found himself to like Wei too, and the two started dating.
During the rest of their college life and relationship, Xiaozheng and Wei found that they have starkly contrasting personalities. Although he appreciated Wei’s fiery enthusiastic personality, Xiaozheng also reprimanded Wei at times for her laid-back and undisciplined attitude towards her coursework. Wei asked Xiaozheng why he was always so serious about everything. Xiaozheng replied, “I don’t know what your attitude towards your life is, but my life is like a building that can only be built once, so I cannot afford any margin of error, not even a centimeter’s width.” Due to his family’s modest financial circumstances, Xiaozheng felt that he needed to do anything and everything he can to ensure the best possible professional future for himself.
Eventually graduation came upon Wei and Xiaozheng. At the on-campus recruitment and interview fair, Wei hoped she and Xiaozheng could find work at the same institute, thus remain together. Unbeknownst to Wei, Xiaozheng had applied to and obtained a graduate fellowship to study architecture in America. When Wei finally learned of his plan, she confronted Xiaozheng to ask why she was the last one to know. Xiaozheng explained that he could not tell her because he was afraid of hurting her and reiterated that he could not make any mistake in his life, thus he had to make this choice of leaving her to make a better future for himself.
A few years later, Wei became a mature professional who excelled in her work, much different from her bygone youthful days. One day she suddenly encountered Lin Jing. Jing explained that he left abruptly then because he learned his father was having an affair with Wei’s mother, so he could not face Wei. He never went to America, but avoided contact with Wei. The one time when he saw Wei on at her campus, she was happy with Xiaozheng. Now however, he wanted to come back and rekindle their friendship and, if possible, romance. At this time, Xiaozheng also returned from America as a renowned and accomplished architect. Though he had everything professionally that he was determined to get, Xiaozheng found the life that he had gained empty and crippled. He deeply regretted letting go of Wei, realizing his time with her was the only time he could be his true self, thus he also wanted to rekindle their relationship. However, Wei on their first meeting firmly rejected Xiaocheng. Not long afterward, Ruan Guan was killed in a car accident when trying to meet her university boyfriend one last time before she marries another man. Wei, in grief, asked Lin Jing to marry her. However, she later called it off when Lin Jing told Wei about another girl that loved him during their time apart. Afterwards, Xiaocheng and Wei met once more at the aquarium to reminisce. There Xiaozheng asks Wei, “Can I start over, and love you again?” to which Wei replies, “Xiaozheng, we spent our youth together, we owe each other nothing… youth is something you can only relive in memory.”