Yoshimori Sumimura is a 14-year-old student at Karasumori School. Following in the tradition that's come down through the generations, he is the twenty-second Kekkaishi of the Sumimura clan. But he’s constantly fighting with his rival, Tokine Yukimura—his childhood friend and also a Kekkaishi—about who is the rightful heir to the magical barrier arts. Protecting people from danger while growing stronger himself, Yoshimori will battle the forces of evil again tonight!
Yoshimori's brother Masamori has loads of advice for his little brother, but whether or not Yoshimori takes it remains to be seen. Then a mysterious kekkaishi named Gen shows up at the Karasumori site to help out, and Tokine has her hands full keeping Gen and Yoshimori focused on fighting ayakashi instead of each other!
A group of Ayakashi disguised as humans breaks into Karasumori Academy, and Yoshimori, Tokine and Gen must go into full battle mode. Furious from the repeated attacks, Gen takes a risky step that ends up in his being discharged from his duties. Yoshimori goes to plead his case before Masamori and learns more about Gen's troubled past.
To defend Karasumori from the Kokuboro, Masamori's Night Troops move into the Sumimura residence. Meanwhile, Yoshimori is bent on revenge and even allows himself to be captured in order to be led back to Kaguro. But he'll have to face the cruel Byaku and an intricate castle maze before finally tracking down the one he came to destroy.