TV-Series
Description
Berta Kastner, designated agent 009-4, operates as a cyborg intelligence agent within the Western Bloc's Number Nine Group under direct command of Number Zero. Her assignments frequently involve collaboration with fellow agents Mylene Hoffman (009-1), Vanessa Ibert (009-3), and Mia Connery (009-7), focusing on missions critical to the prolonged Cold War conflict.

Her background stems from a childhood of poverty as the child of poor immigrants. She gained recognition as a highly active athlete before suffering severe injuries in a traffic accident. The Zero Zero Organization intervened, offering cybernetic limb reconstruction in exchange for her service as an intelligence operative, which she accepted. This transformation established her as a specialized combat cyborg, a "human weapon" with integrated firearms and ammunition storage systems distributed throughout her cybernetically enhanced body. Her physical modifications include tactical units within her elbows and knees, adaptable to mission requirements, making her the most extensively cybernetically modified agent in her group. These alterations position her as a direct homage to Albert Heinrich (004) from *Cyborg 009*, emphasizing spy gadgetry over conventional weaponry, with exceptions like rocket launchers integrated into her knee joints.

Her documented missions include a joint operation to extract Russian defector Zond Soyuz, who possessed destabilizing energy source technology. During this infiltration of an Eastern Bloc stronghold, she faced adversaries Ivan Godunov and Lyudmila Schindler. While the team secured Soyuz's invention to prevent its use in sabotaging a lunar disarmament summit, they failed to rescue the scientist. This operation exemplified her role within team-based missions, contrasting with the more solitary assignments of agents like Mylene Hoffman.

Her narrative spans four episodes of the 2006 anime adaptation, originating in supplemental materials released with the Japanese DVD sets that detailed her backstory and operational profile. Within the series' lore, she maintains professional relationships with other Number Nine Group agents, collectively inspired by the abilities of the *Cyborg 009* team. Her physical appearance includes a noticeably darker skin tone.