Born to a Native-American mother possessed by the spirit of an Onikuma she put out of its misery and a Japanese father famous for his skill as a martial artist, Nita Takenaka inherited her mother's curse when she died giving birth to her, becoming a half-demon child who could transform into a monstrous Yōkai when angered. To curb her demon-like temper and moderate her inhuman physical prowess, her father trained her to be a disciplined martial artist and encouraged her to take up baseball as an outlet. Though Nita soon established herself as a talented fighter and an all-star athlete, her demonic instincts also prompted her to become something of a delinquent who would often terrorise her town's populace with her wayward antics.

When her father fell terminally ill and died, Nita was left an outsider in her own homeland without anyone to support her. Feeling somehow responsible for her father's fate, Nita swore to make him proud by becoming the strongest fighter in the world and finally controlling her demonic side. Armed with an unbreakable baseball bat powered by half a demon's spirit and her trusted motorcycle, Nita journeyed to the West to return to her late mother's roots and use its bustling population of metahumans to get stronger. Though her demonic nature sometimes gets the best of her, she has usually been a force for good wherever she goes. Single-minded, nomadic and, oftentimes, nameless, she is known in stories as the Bearzerker -- The Onikuma Girl!

Though physically strong and earnest, Bearzerker's rather obvious lack of intelligence and naivete has made it possible for local crime boss Sanji Salvitori to manipulate her into becoming his top enforcer and the leader of her own bear-themed street gang -- The Berenstain Boys. Too wrapped up in the numerous opportunities to prove her strength, the free food, a new sense of family and the chance to indulge her demon side through reckless criminal acts, Bearzerker has no clue she's being controlled to fulfill Salvitori's selfish goals and ignorantly goes along with her "grandfather's" evil schemes.