Reina shares her childhood in the Land of Asura with her elder brother Souga and Raoh. The trio later fled their homeland, an escape ending at Cassandra prison fortress where Souga sacrificed his leg to ensure Reina and Raoh reached safety.

Within Raoh's King of Fist's Army, Reina serves as Captain of the Royal Guards. She earned the epithet "Reina of the Twin Blades" for mastering the Twin Blades of Sun and Moon style, fighting with two swords simultaneously. Her duties focus on protecting Raoh and executing his strategic commands, often working alongside Souga, the army's chief strategist.

Reina holds unwavering loyalty to Raoh's goal of imposing order through conquest. However, she sometimes questions the harsh methods used, like when Raoh euthanized a foal shielded by the stallion Kokuoh at the Valley of the Black King. Reina initially saw cruelty, later understanding it as mercy to free Kokuoh for battle. Her protective instincts surge when Raoh faces grave threats, such as his duel with Thouzer.

This commitment is further tested when Juda's subordinates capture her. Raoh personally storms the enemy stronghold to free her, his reaction blending restrained admonishment for her vulnerability with clear relief at her safety, revealing their deep, complex bond.

Reina maintains sharp awareness within Raoh's inner circle. She alone knows Sakuya secretly visits Raoh's brother Toki at Cassandra to relay intelligence on Raoh and Kenshiro. Reina observes these covert actions but chooses not to expose them, suggesting strategic patience or a deeper understanding of potential consequences.

Witnessing Raoh's rise, Reina evolves from a loyal subordinate bound by shared history into a discerning observer. She sees the escalating brutality of empire-building, occasionally reflecting on its moral cost while remaining steadfast in her foundational role. Her character embodies the tension between personal devotion and the harsh realities of consolidating power in a lawless world.