In the 24th Century, Intergalactic Space Travel has become a reality. One of the first outposts in the far reaches of space is WATCHER'S NEST - an inflation hole drive portal - which has recently come under attack by a mysterious force known simply as GHOUL... A group of young female cadets assigned to the portal are unexpectedly thrown into a hornet's nest of trouble as they finalize their training to become an elite pilot in the Seraphim Squadron. (Source: DVD Collection Back Cover)

Equipped with cutting-edge weaponry and specialized troops, a private military organization named Mithril strives to extinguish the world's terrorism and all threats to peace on earth. The organization is powered by the "Whispered," individuals who possess intuitive knowledge and the remarkable ability to create powerful devices and machinery. Seventeen-year-old Sousuke Sagara, a sergeant working for Mithril, has been assigned to protect Kaname Chidori, a Whispered candidate. He is ordered to join her high school class and be as close to her as possible to prevent her from falling into enemy hands—that is, if he can safely blend in with their fellow classmates without revealing his true identity. Sousuke, who was raised on a battlefield and has very little knowledge of an average high school student's lifestyle, must adapt to a normal school life to safeguard Kaname. However, enemy forces have already begun making their move, and Sousuke is about to find out that the adversary coming for the Whispered girl may be a lot more familiar than he expects. [Written by MAL Rewrite]

After overcoming various tumultuous events, mercenary sergeant Sousuke Sagara of Mithril and "Whispered" school girl Kaname Chidori return to their normal high school lives. Sousuke continues his efforts to assimilate with the civilian population and manage his mission at the same time, while Kaname attempts to support his endeavors (even though his antics often drive her up a wall). However, as their lives calm, new problems begin to appear. The appearance of an independent terrorist organization known as Amalgam and internal conflicts within Mithril threaten to wreak unity into a series of failures and betrayals. And new, powerful Arm Slave models only worsen the situation when the world's peace is at stake. As Kaname and Sousuke face their own inner battles amidst life-threatening fights, will they be able to make the right choices and change their future? [Written by MAL Rewrite]

The boisterous student Kaname Chidori and soldier Sousuke Sagara are enjoying a blissful high school life. However, their peaceful days are disrupted by the threatening terrorist organization Amalgam. Leonard Testarossa, a member of the organization who possesses "Whispered," seeks to procure Kaname and her knowledge. Kaname and Sousuke's battle against Amalgam starts right in their own neighborhood, which eventually takes them on a hunt around the world. From the exotic lands of Laos to the barren Mexican coast, Sousuke must gather intelligence to bring down Amalgam. Meanwhile, Kaname's abilities grow, but so does her frustration as her resolve withers. Caught up in an intense game of hide and seek, as well as strategic plots, the pair try to connect and push beyond their own limits. [Written by MAL Rewrite]