In a world where high school life collides with covert military operations, a young soldier finds his most challenging mission is protecting a seemingly ordinary girl. Voiced by Tomokazu Seki, Sousuke Sagara is a battle-hardened mercenary from the secretive organization Mithril, assigned to guard Kaname Chidori, a spirited high school student played by Satsuki Yukino. Unbeknownst to her, Kaname possesses a mysterious and powerful knowledge that makes her a target for shadowy forces. Sousuke, whose entire life has been war, must now navigate the bewildering terrain of classrooms and teenage drama while concealing his true purpose. This explosive feature film, directed by Koichi Chigira, masterfully blends intense mecha combat with unexpected comedy and tender romance, as Sousuke's rigid military discipline is constantly upended by the chaotic normalcy Kaname represents. As the threat to her life escalates, he must confront the ultimate question: can he complete his mission without losing his own humanity in the process?