Reito lives with his older brother Shiro in the desert settlement of Oswald, both afflicted by a degenerative neurological disease plaguing their people. He displays a protective nature, chastising Lena Sayers after she punches Shiro for accidentally seeing her bathe. Reito shares a close bond with Shiro, who searches for a cure. Shiro later instructs Reito to return to their village alone, highlighting their relationship and shared burden. Narrative implications later link Shiro to Lena Sayers, making Reito the future uncle of Arika Yumemiya.

Reito's disease progresses, forcing the transplantation of his nervous system and brain into a mechanical body to survive. He becomes the cyborg known as Rad, affiliated with the Aswad organization. A photograph shows him alongside a younger Yohko Helene, confirming his past human identity. When Yohko confronts him using the name Reito, Rad rejects his former self.

In the manga continuity, Rad appears as a "Perfect Cyborg" created through Schwarz's forbidden "Black Science," retaining only his nervous system and some internal organs as organic matter; his transformation is not attributed to the Aswad plague. He initially serves as an antagonist, attempting to assassinate Mashiro during an attack on the Artai embassy in Windbloom. Rad demonstrates formidable combat prowess, capable of cutting artillery in half and battling the robed Shizuru.

A major manga revelation occurs when Rad claims to be Arika Yumemiya's biological father. Flashbacks imply a past relationship with Lena Sayers before her Otome career and his cybernetic conversion. Despite his earlier antagonism, Rad experiences a change of heart, protecting Mashiro from Akira and encouraging him to become a good ruler. He sacrifices himself to save Mashiro from an attack by Cardair's Scale Sisters Otome, allowing himself to be stabbed before initiating a self-destruct. Before dying, he asks Mashiro to be a worthy monarch and urges Arika to become a "star of hope," leading Arika to acknowledge him as her father.