Born to a hard Matsu line, Kiyo was raised between blood and fur, learning the ways of war alongside the habits of beasts. While her mother hoped to lead the girl in the ways of the Berserkers, from an early age, animals responded to her more readily than people ever did, and her temper and instincts marked her as a natural fit for the Beastmasters. Battle honed her body but did little to soften her manner. She remains blunt, impatient, and uncomfortable around people, especially in formal settings.

Stationed in the City of Rich Frog, she follows her duty and very rarely mingles with samurai of other clans.

Away from watchful eyes, Kiyo nurtures habits that do not fit the image of a Lion warrior. She reads frivolous romance stories, spends long nights stargazing, and loses herself in quiet daydreams about lives less constrained by duty. She prefers the company of animals, finding their honesty easier to endure than human expectations, but when she does grow close to others she does so quickly and deeply, often more than is wise.

She is not often seen without full armour, yet the strands of unusual strawberry-blonde hair can be sighted peeking from under her helmet.