Ragna is the main protagonist of Ragna Crimson. His early life was marked by repeated tragedy: at the age of three, his parents were killed and eaten by dragons, and relatives who later took him in were also devoured. He was subsequently sold to a wealthy family, only for their mansion to be burned down by dragons as well. These events gave him a reputation for being cursed, and he was frequently mocked, ostracized, and even beaten by others. The prodigy dragon hunter Leonica eventually rescued him and, seeing a hidden strength in his ability to survive such misfortunes, invited him to become her partner. For years, Ragna served more as her squire and caretaker than as a capable hunter, quietly training in secret with the hope of one day being strong enough to protect her rather than being a burden.

In terms of personality, Ragna is initially weak-willed and prone to following others and letting himself be ordered around. He genuinely believes he is cursed and that the tragedies around him are his own fault for being too weak. He also feels uneasy in large groups, partly from a habit of keeping his distance so that others will not suffer what he sees as his misfortune. Despite this, he is deeply devoted to Leonica and is willing to risk his life for her. After inheriting the power and memories of his future self, his demeanor shifts dramatically: he becomes cold, efficient, and singularly focused on exterminating every dragon in the world, while remaining socially awkward and emotionally scarred by the traumatic future he has seen. He does not believe the ends justify the means, yet he maintains that anyone who travels with him must be either someone whose death would not affect him or someone who cannot die at all.

Ragna's central motivation is preventing the future that his older self experienced, a timeline in which Leonica and everyone he cared about were killed. This desire to protect what his future self lost drives his obsessive quest to wipe out the entire dragon race, including the powerful dragon monarchs and the Dragon God. In the story, he plays the role of the single most important human weapon against the dragons. After receiving his future self's power, he destroys the dragon horde attacking his hometown, saves Leonica, and forms an alliance with Crimson, a former dragon king turned traitor, to pursue his goal.

His key relationships shape much of his journey. Leonica is the person he cherishes most, and his decision to leave her behind for her own safety devastates her, though she refuses to remain protected and continues fighting to catch up to his level. His alliance with Crimson is pragmatic, tense, and mutually manipulative: Ragna distrusts Crimson but relies on Crimson's strategic mind, and he even drinks a poison offered by Crimson as a condition of their partnership. He also allies with Starlia Lese, the leader of the Silver Armaments Corps, who becomes fascinated by the purity of his silver light and supports him in the war against the Winged Bloodline. Over time, Ragna grows from a self-deprecating weakling into a fearsome and efficient killer, and his development involves learning to lead others, such as the corps under the Silverware Princess, rather than fighting a lonely war of attrition, while struggling to preserve his humanity against the overwhelming power that threatens to consume his body.

Ragna's notable abilities come from the memories and power granted by his future self, which include decades of combat experience, deep knowledge of dragons and their weaknesses, and mastery of aura control. His body has fused with a silver sword, allowing him to produce silver aura, known as silverine, naturally. This grants him resistance to magic and the ability to manipulate silver aura to freeze and nullify magic, amplify his physical capabilities, forge weapons, and enhance objects with silver attributes. He is a master of the Silver Battle Arts and is considered one of the best users of silver aura. Because his body is effectively part silver sword, he can alter its form, turning limbs into blades, and can restore or reforge damaged parts, such as reattaching his head after being beheaded. He also wields the Silver Comet Sword, which provides a significant power boost and additional abilities. His access to future knowledge is not automatic, as he must encounter specific clues to unlock those memories. Additionally, he carries traces of a failed blood ritual from his future self, leaving him partially connected to the Winged Bloodline. His use of this immense power also causes accelerated aging, visibly maturing him over the course of the story.