Kazuki, also known as Kazuki the Black Tone, is a master markswoman and legendary gunfighter who appears in the second season of the anime. She is famous for her exceptional skill with firearms, which she demonstrates through her use of two shotguns. Her most notable ability is the power to manipulate the trajectory of her bullets at will, allowing her to shoot enemies even when they are hiding behind cover. Combined with her remarkable agility, this makes her a formidable and deadly opponent in combat.

Kazuki has a storied past that contributes to her legendary status. She single-handedly liberated a city in northern Japan that had fallen under the control of a self-proclaimed Demon Lord, an achievement that cemented her reputation as a powerful warrior. In addition to her combat prowess, she possesses an incredible singing voice, adding another dimension to her character.

In the story, Kazuki makes her way to the Free City of Okafu for reasons that are initially unclear. Her arrival draws the attention of the mercenaries operating in the city, including Shalk the Sound Slicer, a character from the first season who has become a hired gun in Okafu. The mercenaries, with Shalk among them, join forces to hunt and kill Kazuki. Despite her formidable skills and agility, she is ultimately no match for Shalk, whose speed proves to be far greater. This confrontation leads to her swift demise, ending her potential role in the larger conflicts of the series.