Sousuke is an approximately 17 year old [2] sergeant within the paramilitary counter-terrorist force, Mithril. He is a member of the SRT (Special Response Team) of the Western Pacific Battle Group "Tuatha de Danaan" aboard the assault submarine of the same name under the command of Captain Teletha Tessa Testarossa. His call sign is Urzu-7 and his ID number is B-3128, and operates as team pointman as an Arm Slave specialist.

In addition to being a capable Arm Slave pilot, Sousuke is a specialist in Arm Slave operations and maintenance, improvised explosives, small arms, survival training, anti-armor combat, trap setting and camouflage. Additionally, he is proficient in logistics, demolitions, breach and forced entry, covert intrusion, and hand to hand combat. His background and experience as a guerrilla fighter, and later a mercenary soldier has made him much more sensitive and knowledgeable about tactics and methods more commonly used by guerrillas than government trained regulars.

Sousuke is unfortunately not very good at social interaction off the battlefield. He constantly causes many problems for Kaname Chidori due to his military nature. Even in school he carries a gun with him although it is loaded with non-lethal rounds. He is also very bad at blending in with normal members of society due to his nature (i.e. following Kaname with stalker-like aspects and jumping off a train to follow her). That is, he has no readily available "civil" concepts about life, like entertainment or anything recreational and tends to horribly misinterpret the actions of people around him (like considering a guy who dumped his girlfriend a high-level tactician who is to be reckoned with). This is shown throughout the main series in multiple episodes, and the Full Metal Panic? Fumoffu! series focuses mainly on this aspect. This part of his personality is indeed one of the main sources of the series' humour.

Kaname is the main female protagonist of the story, and appears to be a "normal" 16 year-old high school student at first glance. The character was taken from a friend of the authors, whose name was also Kaname Chidori, living in Japan. The discovery of her Whispered abilities attracts the attention of terrorist organizations. As a result, Sousuke has been assigned by Mithril to protect her. While Sousuke Sagara's battle intuition generally saves her from dangerous situations, she often considers Sosuke's instincts an irritant in daily high school events, leading to countless comical situations. Nonetheless, she and Sousuke continue to grow closer, to the point where they have expressed their feelings for each other.

Kaname's Whispered abilities also grant her an inherent knowledge (but not necessarily understanding) of advanced mathematics and science. It is no surprise then, that she consistently achieves top scores in these subjects at school. Her abilities as a Whispered, however, are a bit buggy. She does not know her full abilities, and also sometimes enters a near-trance, where she understands Black Technology completely.

After a point in the series, she makes it obvious to herself that she likes Sousuke, but that doesn't stop her from hitting him with her harisen. Kaname is very easy to anger, especially considering Sousuke's antics. A humorous comment made by Kurz Weber about her anger was when he saw her lose her temper and commented, "What happened to my angel?" A majority of the stunts pulled by Sousuke will cause Kaname to go into a rage fit and either hit Sousuke or chew him out. However she has a soft spot for him and when he does a good job she will often cook for him or give him a compliment.

Kaname is constantly battling with Teletha "Tessa" Testarossa for Sousuke. Although the two usually end up making either fools of themselves or hurting Sousuke.

Kaname's bravery and determination came to a head in the climax of the novel Continuing on My Own. Following Sosuke's defeat by the hands of Leonard Testarossa, she gives herself up to Leonard and Amalgam to save his life. As she is picked up by the Belial's giant hand, she whispers something to Sousuke before being whisked off. After being taken by Leonard, she was imprisoned at an island villa by Amalgam. In the novel, Come Make My Day, Sousuke arrives at the island in order to save Chidori, but is unable to do so, because she's taken away in a helicopter. During the flight, Kaname is able to communicate with Sousuke, and that's when they both confess their feelings for each other, and Sousuke promises Kaname he'll find her no matter what the cost is.

She also developed feelings of guilt in the novel End of Day by Day (anime: The Second Raid) at having missed her opportunity to kiss Sousuke -- after personally giving him a haircut -- and thus having her first kiss "stolen" by Leonard Testarossa, as well as missing numerous opportunities afterwards to admit her feelings of love to Sousuke. At the end of the novel Come Make My Day she finally expresses those feelings to Sousuke while in radio contact with him and extracts an absolute promise from Sousuke that they will kiss the moment they are reunited.

In the most recent novel, Semaru Nick of Time, the origin of the Whispered is discovered to be from an accident during a Soviet experiment using an "Omni-Sphere" that occurred on December 24, 1984 -- when all the Whispered were born. Leonard Testarossa takes Kaname back to the Omni-Sphere after recovering from his wounds in Come Make My Day. There she is forced to resonate with Sophia, a key Whispered, who overtakes Kaname's personality. Under Sophia's control, Kaname is shown the illusion of shooting and killing Tessa Testarossa and Sousuke Sagara. Under Sophia's control, she leaves with Leonard for Merida Island, where Amalgam has built a machine to utilize a final ability of the Whispered; her soul crushed believing she killed her good friend and the man she loves.

Kurz is a member of Mithril and has the rank of Sergeant in the SRT (Special Response Team) of the TDD-1 Tuatha de Danaan Pacific Battle Group. He has the call sign Urzu-6 and his ID number is B-3127. He is an SRT Arm Slave pilot and designated marksman, equally proficient with sniper rifles and Arm Slave long range precision cannons. It is said he can visualize the exact trajectory of a bullet, resulting in an almost inhuman accuracy. He most often forms a three-man cell with squadmate Sousuke Sagara and squad leader Melissa Mao. He is regarded as a finicky genius, burdening the Mithril mechanics with extremely difficult to understand complaints and requests.[3]

Kurz is a Caucasian male, roughly six feet tall. He is of German decent, and sports a blond mullet and has blue eyes. He is very good looking, and combined with his outgoing personality easily befriends most people. His reputation with women in romantic terms is largely spoiled by his unflinching and overdone pursuit of "the fairer sex".

Kurz can speak Japanese, English and German fluently. He had aspirations of becoming a professional blues singer before he was a soldier. From this, Kurz can sing and play the guitar quite well, entertaining the ersatz hostage Jindai High students with his rendition of "Take me out Mariana Trench!" in the novel, A Dancing Very Merry Christmas!.

In the scope of the main anime and novel series, Kurz is shown being deployed in Tokyo with Melissa and Sousuke in protecting Kaname Chidori. During the course of the show, he displays his extreme talent with a WA2000 rifle. A notable shot is made from a back of a moving truck into the open gun port of the 30mm GAU-8 Avenger cannon of the Behemoth. Later, Kurz assists Sousuke in subduing John Danigan and Guen Bien Bo, two SRT members turned defectors after Gauron had hijacked the Tuatha de Danaan. His hand to hand combat skills in this incident are harshly judged as being “worse than a city punk” by Melissa Mao.

He is known to be a hard hitter on women and speaks in vulgar and flippant language. Despite the negative attitude he has received from women, he is still Sousuke's best friend from Mithril. Kurz annoys Melissa Mao greatly due to the open nature of his sexual feelings for her. In essence, he is Sousuke's complete opposite in personality.

At the time of the novel "Dancing Very Merry Christmas!", 1st Lieutenant Grouseax and the newly-promoted 2nd Lieutenant Melissa Mao placed him under observation for promotion to Sergeant Major. In the serialised novel "Tsudou to Make My Day", Kurz is the SRT's Sergeant Major.

His alias is Kalius, a name he used during the snatch operation on Vincent Bruno.

Kurz's status in the Full Metal Panic universe is currently in limbo. In the most recent novel, Semaru Nick of Time, it is revealed that Kurz and Mao had finally entered into an intimate relationship (even engaging in sex multiple times in a single day). It also appears that at the end of the novel Kurz is killed by the sniper Casper, the man who trained him in sniping and is now working for Amalgam. As Kurz's body was not recovered, it is assumed he died, but it may be revealed in subsequent novels that he survived.

Serving as the SRT's second-in-command next to Gail McAllen, she serves in Mithril under the call sign Urzu-2. Her expertise in electronic warfare is valued by the Pacific Battle Group Tuatha de Danaan. Her rank was Sergeant Major, but by the novel Continuing on My Own she has been promoted to Second Lieutenant, making her a commissioned officer. She is 25 years old.

Melissa is very proficient in use of an Arm Slave, however she lacks exact control. She tends to use fast and furious methods in her firearm use. Later in the series she usually does not pilot an Arm Slave, but she can still pilot excellently, although her capabilities are nowhere near those of Sousuke Sagara and Kurz Weber. Aside from English, she can also speak fluent Cantonese due to her time spent in Hong Kong, particularly in Kowloon.[5]

Melissa is a ruthless insulter and an extremely heavy drinker, somewhat reminiscent of Misato Katsuragi from Neon Genesis Evangelion who is also voiced by Alison Keith. She is shown once having many cigarettes and a minimum of 20 beer cans sprawled out on Tessa's coffee table. She is extremely rude, preferring to use heavy language when talking to someone angering her or someone she can not stand. During the Full Metal Panic? Fumoffu! episode in which Sousuke is training rugby players, he is shown using extremely heavy language based on the training manual Melissa gave him—language inspired and quoted from R. Lee Ermey's lines in Full Metal Jacket; appropriate, since Mao was a Marine Corps drill instructor. She also enjoys a practical joke or two. Once in the series when Sagara called to protest Tessa's staying in his apartment, she gave him permission to "jump her bones", obviously aware of Tessa's feeling for him. But in the next episode when Tessa again found herself in his bedroom, Mao was there and she handcuffed Tessa to herself to keep her from sneaking into his room.

Teletha "Tessa" Testarossa is the charmingly clumsy Captain of the revered TDD-1 Tuatha De Danaan submarine of the anti-terrorist organization Mithril. It was created for use in underwater and aquatic warfare against terrorists, smugglers, and military units She is American by birth but has lived on submarines and military bases for the majority of her life. She was born on December 24, 1984[4] and is a child prodigy who rose to such a high rank at the age of only sixteen. She has platinum/silver hair and gray eyes. Later revealed as being a Whispered, her high level of mathematical and scientific adeptness is dwarfed only by her brother's, which seems to have given her a sense of inferiority. Though not very athletically inclined, she has shown to be a very good swimmer (as shown in episode 8 of Full Metal Panic? Fumoffu!). She has an interest in Sousuke that extends beyond a professional one, generating a love triangle she shares with Sousuke Sagara and Kaname Chidori. Even though Chidori and Tessa seem to compete against each other for Sousuke, they are good friends in reality, as during several episodes they talk about Sousuke and his unique military charm. Teletha is also one of the chief designers of the TDD-1 Tuatha de Danaan offensive submarine, and the creator of Dana, the submarine's Artificial Intelligence.