|“||The new race will never prosper! I will kill that girl before that can happen.||”|
–Bando, vowing vengeance on Lucy
Bando, when first introduced, is an operative for the National Police Agency's Special Assault Team (SAT). His combat skills, blood-lust and determination made him one of its top agents. His personality, while normally being highly apathetic, aggressive to the point of sadism and decidedly anti-social, was also driven by a deeply felt sense of honor and obligation.
He and the S.A.T team were sent in pursuit of the recently-escaped Lucy. Finding her as the amnesiac Nyu, Bando rendered first Yuka and then the protesting Kouta unconscious before attempting to engage Nyu in battle. Disgusted when she failed to prove the menace his briefings had spoken of, Bando ordered his junior partner, Satou, to kill her instead.
By this point, the Lucy persona had both mentally and physically woken up. After killing Satou, she had sport with Bando before mutilating him, taking his eyes and one arm, taunting as she went. Reverting to Nyu, she fled, leaving the wounded Bando helpless and enraged, until the then-homeless Mayu saw him, calmed him and called an ambulance on his behalf.
While Bando had the intelligence to understand Kurama when he explained why his encounter would necessitate his castration, he desperately tried to find some alternatives. After an awkward encounter with Nyu outside of the college attended by Kouta and Yuka, Bando heard the opinion of Professor Kakuzawa, but rejected what he correctly saw as the insane pro-Diclonius agenda the Professor put forward.
Determined to avenge himself on Lucy, he agreed to undergo operations to replace his eyes and arm with cybernetic parts, but drew the line at efforts to castrate him in order to prevent any more Diclonius births. Escaping the Doctor's office with the partial connivance of Isobe, he used his SAT membership to build up his ammo before the membership was revoked, focusing his time and resources on a rematch with Lucy. In the meantime, he made alliances (to widely varying degrees) with Lucy's enemies, Nana and Kurama, playing a pivotal role in their struggle against Kurama's daughter Mariko. At one point, Bando stopped the despondent Kurama from committing suicide, even caring for him while he recuperated. It also seems that he was placed in touch with Saseba.
He slowly developed a relationship with the young girl, Mayu, who he grudgingly came to accept, even while maintaining his gruff exterior. Mayu even called on him to rescue her and Nana from the pedophilic Unknown Man, but their relationship nearly ended when he learned that Mayu had lied to him about the presence in the Maple House of Kaede/Lucy/Nyu. Seeking his forgiveness, she got caught up in a battle on the beach between Bando, Lucy, and the Unknown Man. Bando, having wisely scoured the beach to clear it of potential weapons for Lucy, was also able to somehow dodge both direct attacks from Lucy's vectors and many of her most clever indirect attacks, mostly by feeling for vibrations in the air. He also made good use of the crossbow he seized from Unknown Man to place Lucy firmly on the defensive for once. This crossbow would once again turn up in the possession of Saseba's agent inside Kakuzawa's organization.
When Mayu's memories of Lucy's dismemberment of Nana returned, Lucy tried to kill her, only for Bando to take the blow. Lucy ripped off his remaining arm, sliced him in half, and then fled when he managed to shoot off her regenerated horns. As he appeared to die in Mayu's arms, Bandō reflected that he had always wanted someone to cry for him after he died, since he had isolated himself from society his whole life. In his memory, Mayu continued cleaning the beach where Bandō had come to live. In the last chapter, Bandō is seen approaching Mayu on the beach, telling her there was no way he could die. She tearfully ran toward and embraced him. A close-up shot of his foot and lower torso seemed to indicate that he was resuscitated through the use of bionics, although no definite explanation is ever given. It was possible that Kurama's connections aided in this. His wish had failed, however, since he had lost his lower body, he could no longer reproduce.
Mayu's feelings for Bando were perhaps parental, perhaps romantic. His feelings for her, while real, were not truly spoken of, but he seemed to have at least reciprocated.
In the Anime's final episodes, Bando was allied with Kurama, a deal made to repair his cybernetics, damaged in battle with Nana, in exchange for killing Mariko. Mariko is recuperating when Bando arrives, and instead he targets Lucy, seeking revenge. It seems like he survived another (off-screen) defeat at her hands. Lucy claimed that he will never see her again as she left him alive. It is unknown if a second anime season would have included another confrontation. Also, in the anime as presented, he never develops a relationship with Mayu, and the two never see each other again after their first reunion following his return to the beach. Again, whether this would have warmed up in a second season will likely never be known.