Princess Ouni, also known as Shuten Dōji, originates from the Kai Doh Maru OVA narrative, reimagining Japanese folklore elements. She is Kintoki's cousin, sharing a familial background rooted in the Shōryaku era. Her uncle's violent coup, aimed at seizing control of their family, murdered Kintoki's parents and nearly executed Kintoki, forging Ouni's early connection to betrayal and power struggles.

Five years later, in the Chōtoku era, Ouni reemerges as the bandit leader Shuten Dōji, reigning from Mount Ōeyama. Her transformation into a demonic figure aligns with folklore depictions of Shuten Dōji as an oni commanding outlaws. She orchestrates attacks on Kyoto, collaborating with the political schemer Fujiwara no Michinaga to exploit the capital's instability caused by rampant disease and civil unrest. Her actions include burning the city, intensifying the chaos to further Michinaga's goal of seizing governmental control.

Ouni's motivations intertwine personal history with political ambition. Unaware Kintoki was raised disguised as a boy, she believes her cousin is the displaced male heir. Seeking to "rescue" Kintoki from Raikō's influence, Ouni abducts her after a confrontation with Raikō's warriors. This abduction prompts Raikō's pursuit to her Ōeyama stronghold, setting the stage for their final clash.

Her character embodies a tragic duality: a princess-turned-demon whose rebellion against familial and societal constraints fuels her descent into villainy. She stands as both a product of her uncle's treachery and an architect of Kyoto's downfall, bridging personal vengeance with broader political manipulation.