Mamoru Sakimori, better known by his alias Captain Bravo, is a veteran Warrior Chief within the Alchemist Army and serves as the dormitory manager at Ginsei Private Academy, where the protagonist Kazuki Muto lives. He is a tall man with brown hair and blue eyes, standing approximately 1.85 meters tall. In his role as an Alchemist Warrior, he typically wears a full-body outfit that covers every part of his body except his eyes, though he does not actually use this to conceal his identity—he appears without the costume when acting as the dorm supervisor.

Captain Bravo initially comes across as serious and mysterious, but his true personality is enthusiastic, exuberant, and openly dramatic. He shares a gung‑ho attitude toward self‑improvement and life in general, much like Kazuki, and is not afraid to strike victory poses or engage in theatrical behavior. He frequently exclaims the word “Bravo” when applauding someone, and he claims to have thirteen different named attacks, such as “Meteor-Bravo Kick” and “Charming-Bravo Kiss.” Despite his outward confidence, he harbors deep sadness over the loss of comrades, though he tries to suppress his emotions on the belief that a warrior’s defeat means death.

His motivations are shaped by a past failure. In his first and only mission as part of the Showusei Team, the operation ended in catastrophic failure, and only a child named Tokiko Tsumura was saved. This event caused Mamoru to abandon his real name out of shame; he instead adopted the flamboyant alias Captain Bravo, claiming it was “cooler” while actually using it to distance himself from that trauma. His primary motivation throughout the story is to protect and mentor those he cares about, especially Tokiko, whom he rescued as a child and treats like a daughter, and later Kazuki, whom he comes to see as a son figure.

In the story, Captain Bravo is initially ordered to assassinate Kazuki after it is discovered that Kazuki’s kakugane is a Black Kakugane that turns him into a Victor. Bravo attempts to kill Kazuki, at one point throwing him off a cliff, but after Kazuki defeats him in battle, Bravo changes course and begins to defend him. Later, during a confrontation with the Re‑Extermination Squad leader Sekima Hiwatari, Bravo sacrifices his own buso renkin, Silver Skin, to shield Kazuki and Tokiko from Hiwatari’s attack. He remains conscious and uses his control over Silver Skin to prevent Hiwatari and Kazuki from harming each other until the situation is resolved by the intervention of Showusei. This act leaves him critically injured but demonstrates his deep loyalty and willingness to give up his own power for others.

His key relationships include Tokiko Tsumura, whom he saved as a child and continues to command; Kazuki Muto, whom he initially opposes but later trains and protects as a father figure; and other Alchemist Army members such as Gouta Nakamura. He also shares a mutual respect with Papillon at certain points. Captain Bravo develops over the course of the series from a man burdened by his past failure and hiding behind a costume and alias to a more openly caring and self‑sacrificing mentor who fully embraces his role as a protector.

Notable abilities stem from his buso renkin, Silver Skin, which manifests as a silvery, malleable substance that can be shaped into armor, weapons, or protective barriers. He can use it to enhance his physical strength and agility, and he is adept at close‑quarters combat. He is also capable of running across water at high speed due to his extraordinary physical conditioning. Beyond his buso renkin, he employs a variety of unconventional techniques and is a skilled tactician. His catchphrase and enthusiastic demeanor serve to boost morale among his allies.