Lieutenant Basil "Buzz" Nyqvist is a central figure in the Parasite Dolls narrative, serving as an officer in the Branch, a secret division of the AD Police in the city of Megatokyo. His background is defined by two profound personal tragedies that have shaped his worldview and professional conduct. Before the events of the story, Buzz was a gifted sharpshooter, but his life was upended when his wife was killed by a rogue Boomer, an incident that instilled in him a deep-seated grief and a fractured perspective on androids. This trauma was compounded by a catastrophic error in judgment: he shot and killed a young child whom he mistakenly identified as a Boomer. This mistake led to his transfer to the Branch and caused him to renounce the use of firearms, despite his exceptional marksmanship skills.

As a result of these events, Buzz's personality is marked by a profound stoicism and a heavy burden of guilt. He carries himself with a reserved and guarded demeanor, often repressing his emotions as a coping mechanism for his past. He is a principled investigator whose tragic history informs his methods; he favors the non-lethal neutralization of rogue Boomers, driven by a philosophical consideration of their possible humanity. His initial reluctance to work with his Boomer partner, Kimball, slowly thaws as he is forced to confront his own prejudices through Kimball's demonstrated empathy and reliability.

Buzz's primary role in the story is as a field operative for Branch, tasked with investigating crimes involving Boomers that threaten society. His core motivation evolves throughout the narrative, shifting from a state of guilt-fueled isolation toward a search for redemption and a hard-won understanding of coexistence between humans and Boomers. His personal and professional journey is explored across the three OVA episodes. In the first episode, his investigation into a narcotics ring targeting Boomers puts him in direct conflict with his own past. The second episode sees his relationship with fellow officer Reiko Michaelson develop, marked by an unspoken mutual tension and a growing rapport. The final episode forces him to reckon directly with his academic legacy, as a thesis he wrote in college is weaponized by a terrorist, testing his ethical boundaries and forcing a final confrontation with the consequences of his past actions.

Key relationships serve as catalysts for Buzz's character development. His partnership with Kimball is central, as the android's very existence challenges Buzz's trauma-rooted prejudices and forces him to see past the label of "machine". His dynamic with Reiko Michaelson offers a connection that hints at the possibility of moving forward, while his former romance with Agent Angel provides a background of workplace history and unresolved feelings. While he possesses no superhuman abilities, Buzz is noted for his sharp investigative mind and his past as a highly skilled marksman, a talent he largely suppresses due to his guilt over the shooting incident. His journey moves from this place of deep emotional wounding toward a more nuanced perspective on justice and humanity in a world where the line between the organic and the artificial is increasingly blurred.