A story about the youth of this millennium follows a group of students who encounter ups and downs in the marathon of life. Ma Tian who comes from a well-off family and his goody-two-shoes neighbor An Ran transferred to an ordinary high school during their senior year; where they meet different kinds of people — Lao Gou (‘Old Dog’), Da Lijiao, Mimi, Da Zui (‘Big Mouth’) and Song Jie.
On his very first day at his new school, Ma Tian gets into a fight with Lao Gou and each vow to never co-exist with the other. Yet fate seems to be playing a joke on them as they are put in the same marathon team in school. From that time onwards, the two had no choice but to tolerate each other as they are forced to train together all while making each other miserable. It's the last year of high school and these young students undergo countless challenges as they grow in each other's company and mature into adults.