Bando is initially presented as an operative for the National Police Agency's Special Assault Team, known as the SAT. His exceptional combat skills, combined with a pronounced bloodlust and near-total single-mindedness, have made him one of the unit's top agents. In his first appearance, he is portrayed as highly apathetic, sadistic, aggressive, and anti-social, yet he is also driven by a deeply personal sense of honor and obligation.

Bando's primary motivation throughout the story is a relentless desire for revenge. This quest begins after he is sent to recapture the diclonius escapee, Lucy. In their first encounter, he easily overpowers her vulnerable Nyu personality, but the shock of a blow to her head awakens Lucy's true, ruthless persona. In the ensuing battle, Bando holds his own for a time, quickly deducing how to use the two-meter range of her telekinetic vectors against her. However, he is outmaneuvered when Lucy uses a firearm taken from his fallen partner. Lucy proceeds to maim him severely, severing his right hand, breaking his left arm, and gouging out his eyes. She leaves him for dead only when her Nyu personality re-emerges, causing her to flee. This humiliating and debilitating defeat consumes him, transforming his desire for a good fight into a selfish and all-consuming vendetta.

Following this defeat, Bando learns he has been infected with the Diclonius Virus by Lucy's vectors, meaning any children he fathers would be born as diclonius. Facing the prospect of forced castration to prevent this, he escapes after receiving cybernetic replacements for his eyes and lost hand. He rejects a proposal from Professor Kakuzawa to help create a new diclonius race, swearing instead to kill Lucy to prevent such a future. He spends his time preparing for a rematch, often waiting on the same beach where he was defeated, which he meticulously clears of debris to deny Lucy any potential projectiles.

Despite his brutish and violent nature, a more complex personality gradually emerges. He develops a grudging relationship with Mayu, a homeless girl who saved his life by tending his wounds after his first battle with Lucy. Though he maintains a gruff exterior and often reacts with violence, he accepts her presence and even promises to help her if she is in danger. He honors this promise when Mayu calls him for help against a predatory assassin known as the Unknown Man, brutally defending her. He also shows compassion for a broken Kurama, preventing the scientist from committing suicide after the death of his daughter, Mariko, and caring for him during his recovery. This softer side is further demonstrated when he tends to Nana's wounds and, ultimately, when he sacrifices himself to protect Mayu from a lethal attack by Lucy. As he lies dying from wounds that have sliced him in half, Bando reflects that he had always wished for someone to mourn him, a dream he thought impossible for a man who had isolated himself his entire life.

In his role within the story, Bando serves as a persistent threat to Lucy and an antagonistic force, though his goals align him as an uneasy ally to other characters like Kurama and Nana, who also oppose her. His relationships are key to his development. His bond with Mayu is central, evolving from a sense of obligation to a protective, almost paternal connection, even as he remains emotionally guarded. The manga extends his role significantly beyond the anime adaptation, allowing for his full character arc, including his apparent death and final, surprising return with extensive bionic prosthetics. In the anime, his development is truncated, and he ultimately survives another off-screen defeat by Lucy without the same level of closure.

Bando's notable abilities are rooted in his elite SAT training, which grants him peak human conditioning, tactical intelligence, and proficiency with various weapons. After his maiming, he receives cybernetic implants that restore his sight and replace his missing hand, enhancing his combat potential. He favors custom.50 caliber handguns, whose high-velocity rounds are powerful enough to be deflected but can be effective against vector defenses at close range. In his rematch with Lucy, he demonstrates advanced tactical thinking by clearing the battlefield and develops the ability to sense the minute vibrations in the air caused by her otherwise invisible vectors, allowing him to dodge her attacks. This combination of physical prowess, tactical cunning, and cybernetic enhancement makes him one of the few humans capable of posing a genuine threat to a diclonius.