In the early 21st century, a new island named Hizle I. emerged between Hokkaido and Sakhalin. There, a vocational school student named Hino Kagari finds herself caught in a bombing terrorist attack. She is saved by her classmate, Kuroe Mizuki. Inspired by Kuroe's actions during the incident, Kagari decides to temporarily join the "Northern Guard Corps," a group to which Kuroe belongs. The story follows these two girls in a gun action narrative.
