This is the story of Tooru Kokonoe who has enrolled at Kouryou Academy, a school which trains students in wielding Blaze, soul powered weapons to prepare them for the Dorn Agency's special peacekeeping corps. When Tooru is partnered with a mysterious girl: Julie Sigtuna, he finds he has to overcome many hurdles to ensure their teamwork and fighting skills are up to par for the duration of their training.
The story takes place at Koryo Academy, a high school where students manifest a personal weapon called a Blaze, which is a physical manifestation of their soul. The protagonist, Tooru Kokonoe (sometimes “Tor”), enrolls in the academy driven by tragedy: his younger sister was killed, and he wants to gain power to protect others and possibly avenge her. On entering, Tooru discovers that his Blaze is not a typical weapon — instead of a sword, lance or gun like many classmates, his Blaze takes the form of a shield, making him an “Irregular”. Koryo Academy uses a system called Duo — every student is paired with a partner (their “Duo”), who they train, live, and fight together with. Tooru is paired with Julie Sigtuna, a silver‑haired girl from Scandinavia and a very capable fighter.