Boyakki, whose full name is Boyacky Butsukusa, serves as the chief inventor, mechanical engineer, and technology expert for the Doronbo Gang. He is a tall, slender man with a wiry mustache, prominent buck teeth, and a large nose. His typical attire consists of a green uniform that leaves his midsection exposed. His personality is a blend of intellectual brilliance and overtly lecherous tendencies, most notably an obsessive desire for admiration from high school girls. This fixation is a primary driver of his motivations, and he frequently makes advances toward his gang leader, Doronjo, though he is also portrayed as genuinely desiring a mutual romantic connection with someone willing to return his feelings. Despite his vanity and snarky remarks toward others, he maintains a close camaraderie with his fellow gang member Tonzura, who affectionately calls him Boyayan.

Before a life of crime, Boyakki aspired to be a noodle chef in Koriyama. He received a special rolling pin from his high school girlfriend, Ohana, but his culinary skills proved inadequate, relegating him to work as a dishwasher. This failure, coupled with financial hardship and shame over his circumstances, motivated him to turn to crime, leading to his recruitment into the Doronbo Gang and his decision to sever contact with Ohana. In the original Yatterman series, his primary role is designing the gang's giant mechas for their global missions to find fragments of the Skull Stone for their boss, Dokurobei. He also often acts as the strategist for their various get-rich-quick schemes. His creations consistently feature critical flaws, most infamously including easily triggered self-destruct buttons, which lead to repeated defeats by the Yatterman duo and subsequent harsh punishments from Dokurobei.

Despite his role as a villain, Boyakki exhibits a lingering sense of loyalty to his partners. After the original gang disbands, he reconciles with Ohana, marries her, and successfully establishes a noodle shop in Kokubunji. Fourteen years later, during Time Bokan: Royal Revival, Doronjo and Tonzura seek his help for a race. Initially resistant to rejoining them due to his stable life, he changes his mind when his old friends face defeat, aiding their victory and briefly reviving his criminal activities. In the 2008 remake of Yatterman, his backstory as a failed noodle chef remains consistent, while his comedic traits, especially his fixation on high school girls, are amplified. On some occasions, this desire is explored more deeply, revealing a wish for transformation that can be exploited by others. Among his notable abilities, Boyakki is a genius machine builder capable of creating various combat robots from recycled parts. He also employs a versatile multi-purpose weapon known as the Tokkae Gun, which can fire lasers, flue, and adhesive projectiles. His legacy extends into the future in Yatterman Night, where he has long since passed away, but his descendant, Voltkatze, inherits his alias and fights against the oppressive Yatter Kingdom.