Ryo Sanada, known as Ryo of the Wildfire, descends from the historical Sanada ninja clan. Born in Yamanashi Prefecture's remote mountains, he lost his mother in infancy. His father, a wildlife photographer who rejected the Sanada traditions, raised him. This isolated life cultivated Ryo's deep respect for nature and wildlife, fostering friendships with wild animals but few human connections. Frequent paternal absences forced Ryo into early self-reliance, leaving him unfamiliar with urban trends and social norms.

The white tiger Byakuen rescued Ryo from a childhood mountain injury, forging a lifelong bond. Byakuen later proved instrumental in Ryo's selection as the bearer of the Wildfire Armor (Rekka no Yoroi). Under the mystic Kaos's guidance, Ryo underwent rigorous mountain training a year before the conflict with Arago, preparing him to wield the armor embodying Jin (Righteousness/Benevolence). The armor first manifested during a forest fire crisis when poachers threatened him; his selfless desire to save all lives, including the poachers, activated its sub-gear and ignited the "Jin" kanji on his forehead.

Throughout the war against the Dynasty, Ryo served as the de facto leader of the five warriors. He wields twin katanas—the Swords of Wildfire—that combine into a double-bladed weapon for his signature "Sou En Zan" (Twin Flame Cut). The Wildfire Armor draws power from fire sources, granting flame immunity and enhanced physical capabilities. Ryo's defining trait is an unwavering commitment to protecting others, often prioritizing allies' safety over strategy or personal well-being. This self-sacrificial tendency frequently resulted in injuries or exhaustion, yet it inspired deep loyalty and unity among the warriors.

A significant evolution came when Ryo obtained the Armor of Inferno (Kikoutei), a white armor formed by channeling the combined virtues of the other four warriors. First summoned in a climactic battle against Talpa, its planet-destroying potential demands immense spiritual focus and is temporary. Its power damaged his original swords, leading Ryo to acquire the Swords of Fervor from the defeated warlord Kenbukyou. With these, he performs "Chōdandō Senkōzan" (Rage of Inferno), releasing concentrated energy beams. The Inferno Armor lacks intrinsic virtue, requiring balance through the group's collective virtues. It was destroyed during the OVA "Legend of the Inferno Armor" in a confrontation with Mukala and the Black Inferno Armor.

In the "Gaiden" OVA, Ryo travels to New York City investigating murders linked to a possessed armor. Witnessing the death of Runa, a girl seeking justice for her brother, triggers his emotional transformation into the Inferno Armor to defeat Shikaisen. This arc highlights his struggle with urban environments and profound grief over failing to protect civilians. Byakuen remains his constant companion, evolving into an armored form and later merging with the spirit of the black tiger Fuego Negro. This fusion allows Byakuen to carry the Swords of Fervor, symbolizing Ryo's connection to familial loyalty and battlefield resolve.

Ryo's development emphasizes reconciling his isolated upbringing with leadership duties. Initially uncomfortable with social interactions and fashion, he gradually values teamwork and learns strategic patience while retaining core impulsiveness. His relationship with the other warriors evolved from reluctant allies to deep friendships. His innate "benevolent spirit" is acknowledged as a unifying force, occasionally converting enemies into allies. This trait proved crucial in forming the Kikoutei armor and later armors gifted by Suzunagi in "Message".