As a guardian of space-time order, 28-year-old Wang Dadong returns to Bale High School to investigate an anomaly and clashes with King.

This season picks up where Season 2 left off. With the timeline reset and the KO ranking restored, we see the return of some familiar faces from Season 1. Wang Da Dong joins Xiu as a member of inter-dimensional guards. When sudden spikes in fighting power propped up in Da Dong's old high school disrupting the KO ranking, he goes undercover to investigate... as a 28 year-old dropout repeating high school. His first order of business is to reestablish his authority inside the class of KO One. His behavior immediately clashes with the current leader, King. While the class looks on to see who would emerge victorious, the competition for leadership intensifies with new transfer students joining the fray.

After the events of KO One Return, the timeline reset and the KO ranking are restored, and we see the return of some familiar faces from Season 1 and 2. The 28-year-old Wang Da Dong is a member of inter-dimensional guards together with Xiu. Da Dong goes undercover to investigate the unusual spikes in fighting power in his former high school, Ba Le High School caused by an illegal drug, Hell Vision, as a dropout repeating high school student. His first order of business is to reestablish his authority inside the class of KO One. His behavior immediately clashes with the current leader, King. While the class looks on to see who would emerge victorious, the competition for leadership intensifies with new transfer students joining the fray, including Gu Zhan, the KO.3 tied with Lei Ting and Zhi Ge, the secret KO.2, and Li Yan Yan, the KO.10. Throughout the series he eventually bonds (again) with all his new classmates and begins a relationship with Lei Ting.