Voice: Tomokazu Seki

The protagonist of this story.

He's a part of Mithril, a non-governmental mercenary organization that performs operations to mediate military conflicts. He's a remarkable soldier who has lived on the battlefield since he was just a child. He's a part of the tactical department's western Pacific ocean brigade Tuatha de Danaan's ground warfare unit, SRT (Special Response Team). His rank is sergeant​, and his call sign is "Urzu 7." After receiving orders to guard the Japanese high school student Kaname Chidori, he transfers into her school--Jindai High School--pretending to be a normal transfer student. He lives as a high school while protecting Kaname from the terrorist organizaion Amalgam, which is targeting her due to her being a Whispered, a being with hidden powers related to technology still unknown to society. Though he had only known the battlefield, Sosuke begins getting back some of his humanity by spending time living in Japan, communicating with others. He is able to operate the Arm Slaves Savage, the Gernsback, as well as the ARX-7 Arbalest, which contains the AI "Al."

Voice: Yukana

The supreme commander of the tactical department's western Pacific ocean brigade and the captain of the Tuatha de Danaan combat submarine. Her rank is general. Nicknamed Tessa, she is the superior of Sosuke Sagara. Just like Kaname Chidori, Teletha is a Whispered. She's an American with Swiss Austrian and Italian blood running through her veins, leading to her ash blonde hair and gray eyes. Once she leaves the captain's chair, she becomes an unreliable, clumsy girl. Her elder brother is one of the top brass of the terrorist organization, Amalgam.

Voice: Shinichiro Miki

A member of the same ground combat command SRT as Sosuke Sagara. His rank is sergeant​, and his call sign is Urzu 6. He pilots a Gernsback that houses the AI Yukari. He's a German who is able to speak Japanese fluently. His skills as a sniper are top notch, even when riding an Arm Slave. He was a major player fighting off the giant enemy Arm Slave "Behemoth"'s invasion on Tokyo. Kurz is a good buddy of Sosuke's.

Voice: Michiko Neya

A member of the ground combat command SRT. She has risen to the rank of Lieutenant Commander. Her call sign is "Urzu-2," and she pilots a Gernsback that houses the AI "Friday." Sbe is Kurz and Sosuke's superior officer. She's a Chinese-American woman who looks good with a short haircut. She's a reliable woman with bad booze habits. She doesn't exactly have good luck, and has had to escape a variety of dangerous situations on the battlefield as a result.

Voice: Akio Otsuka

A commander of Mithril's tactical department's western Pacific ocean brigade Tuatha de Danaan's ground warfare unit. His rank is Lieutenant Commander, and his codename is "Perth 1." He can sometimes be cold enough to cut off his subordinates in order to make the mission succeed. Sosuke met Andrei in the past when he was the commander of the special forces of the Soviet Union.

Voice: Tomomichi Nishimura

Vice captain of Mithril's tactical department's western Pacific ocean brigade "Tuatha de Danaan." His rank is commander. He has a serious personality, and because of his dedication to strict order, he's very harsh with Sosuke Sagara, who disrupts any and all order around him. He is nicknamed "Duke" due to his ability to command those around him during marine combat, as well as his ability to keep his cool attitude during a skirmish. He can be a very reliable commander when the need arises.

Voice: Aya Uchida

A non-commissioned officer​ stationed on the Melida Island base in charge of communications. Her rank is sergeant. She's a Japanese girl who transferred from the Japanese self-defense force to Mithril.

Voice: Daisuke Namikawa

The head of Mithril's enemy, the terrorist organization Amalgam, and Teletha Testarossa's twin brother. Like Kaname Chidori and Teletha Testarossa, he is a Whispered. He is deeply involved in the development of the "Codarl" and "Alastor" series of Arm Slaves. Despite his thin build, he is extremely skilled in combat, and pilots the powerful Arm Slave "Belial," which can even overwhelm Sosuke Sagara's Arbalest.

Voice: Kazuhiro Yamaji

A mysterious Asian man, though his exact nationality is unknown. Just like Gauron and Gates before him, Kurama is a bitter enemy of Sosuke Sagara. He's a madman who continues to slaughter people in order to complete his plan of capturing Kaname. He's currently trying to quit smoking, and he has carrot sticks in his cigarette case in the place of smokes.

Voice: Tomokazu Sugita

The subordinate of Leonard Testarossa. He pilots the Erigor, an arm slave developed from the Codarl series. He always has a calm disposition, and speaks in a very polite manner. He is very skilled at Arm Slave combat, and is even able to keep up with the Arm Slave "Falke."

Voice: Satsuki Yukino

The heroine of this story. A female high school student attending Jindai High School who is a part of Class 2-4. Raised overseas, she's gorgeous, fit, and the top of her class. She's cheery and quick to take action, but is completely dense when it comes to issues of romance. She's one of the Whispered, beings who have special powers. Because of this power, she is being targeted by the terrorist organization Amalgam She sometimes is able to escape dangerous situations thanks to those same powers, but she also has times when she wavers as to whether to use them or not.

Voice: Ikue Kimura

A classmate of Kaname Chidori with a spacey and innocent personality. Her trademarks are her glasses and pigtails. She's a member of the student council, as well as Kaname's friend she goes to for advice.

Voice: Toshiyuki Morikawa

The student council president. Sosuke Sagara respects him from the bottom of his heart, going so far as to call him "Excellency."

Voice: Rio Natsuki

The homeroom teacher of Sosuke Sagara and Kaname Chidori's class, 2-4. She's also the counselor for the student council. She has a passion for her job, as can be seen when she sometimes puts her own life on the line to protect her students.