Hailing from Neo Kyoto's impoverished Outer-District, Hiyori Tori grew up parentless, enduring significant hardships from a young age. This challenging upbringing fueled her determination to master the card game Build Divide through relentless daily practice, seeing it as her ticket out and into the affluent Upper-District. Her driving goal is to defeat the King in Build Divide, believing victory will grant her wish to shatter Neo Kyoto's rigid socioeconomic barriers.

Despite her difficult past, Hiyori retains a cheerful, energetic, and optimistic spirit, often displaying clumsiness and a deep enthusiasm for historical dramas. During the Rebuild Battle tournament—where participants vie for the right to challenge the King—she identifies the formidable player Teruto Kurabe as a potential mentor. She persistently pursues apprenticeship under him, addressing him as "Master," though Teruto remains reluctant to provide formal training. This dynamic largely places her in the role of an observer and supporter during his matches, yet her determination to learn from him never wavers.

In Build Divide battles, she wields the white Ace and Territory card "Dagrark." Her journey intertwines deeply with Teruto’s own mission. Following Teruto’s climactic, sacrificial actions in Code Black, which resolve his personal conflicts involving his sister Kikka, Hiyori takes up his resolve and mission. This transition propels her to carry forward the struggle against Neo Kyoto’s oppressive system in the subsequent season, Code White, emerging as a new symbol of hope for the city’s future. Her character evolves from seeking personal advancement to embracing a larger role in challenging Neo Kyoto's established order.