At the age of seven, Rio awakened the memories of Amakawa Haruto, a Japanese university student who died in a traffic accident. Along with Haruto’s experiences, Rio gained a maturity and perspective far beyond his years. Despite appearing as a child, his mindset reflects the knowledge and judgment of an adult, making him calm, rational, and adaptable. He often maintains a reserved demeanor, masking his emotions behind a poker face and adopting excessive humility to avoid jealousy or suspicion from others.

Rio is diligent and highly resourceful, quickly learning new skills and adapting to unfamiliar environments. His calculated nature allows him to make pragmatic decisions, such as accepting King Beltrum’s offer to enroll in the Royal Academy despite his status as a commoner. He also actively seeks to expand his knowledge, including requesting training in spirit arts upon reaching the Seirei no Tami.

Although composed, Rio is fundamentally kind and places the well-being of his friends above his own interests. At the same time, he struggles with insecurity, believing that his thirst for vengeance renders him undeserving of happiness, particularly in his relationship with Miharu. This inner conflict contributes to his difficulty in forming close bonds. Nevertheless, he reacts strongly when his friends are threatened and can act with ruthless decisiveness against those who harm them.

By Volume 16, Rio begins to show signs of change in how he views his relationships, influenced by the trust and affection of the companions he considers family. His perspective softens as he acknowledges the importance of preserving the bonds he has formed, signaling a gradual shift from isolation toward acceptance.

As Rio, his most distinctive feature is his black hair, a rarity outside the Far East, paired with caramel-colored eyes. His androgynous features set him apart from the other orphans in the Beltrum slums. Over time, he matures into a handsome young man with a slender yet toned build, marked by numerous scars from his harsh upbringing.

In his alternate persona as Haruto, he appears with gray, asymmetrical hair that is longer on the right side of his face. He has sharp facial features and serious eyes, exuding a composed and collected presence that conveys both danger and reassurance.

Following his spirit assimilation with Aishia at the end of Volume 20, Rio’s appearance largely resembles that of Haruto, with several notable changes. His eyes shift from caramel to crimson, his hair turns white, and the scars from his childhood are completely healed, giving him a more ethereal and striking appearance.

Rio was born in the Beltrum Kingdom to Zen and Ayame, immigrants from the Yagumo region in the Far East. His father, Zen, was an adventurer who died around the time of Rio’s birth after being betrayed by his companion, Lucius. Following Zen’s death, Rio was raised solely by his mother. Although their black hair often drew prejudice, Ayame’s warmth and resilience allowed Rio to experience a brief period of peace and affection in his early years.

At the age of five, Rio’s life changed irreversibly when Lucius murdered Ayame in front of him. Orphaned and left with nothing, Rio was cast into the slums of the Beltrum capital, where he endured abuse and servitude under a local gang. Stripped of family and security, he swore vengeance against Lucius, vowing to one day take retribution for his mother’s death.

Two years later, at the age of seven, Rio regained the memories of his previous life as Amakawa Haruto, a Japanese student who died in a traffic accident. The fusion of Haruto’s memories with Rio’s consciousness marked a turning point in his survival, granting him new insight and knowledge on the same day his suffering in the slums was about to culminate in death.

Magical Abilities
As the reincarnation of the Dragon King, Rio possesses limitless odo (magic essence). This vast reservoir of energy was first recognized by Dryas during his stay in the Spirit Folk village, and later confirmed by Aishia, who described his essence as bottomless.

Rio demonstrates mastery over Spirit Arts, a system of magic he initially accessed by mimicking magical principles despite failing the formal contract ceremony. He learned techniques such as healing, strengthening, and hypnosis, surprising even experienced users like Ursula. Rio is capable of wielding all elemental attributes, making him highly versatile in combat.

Through his Spirit Contract (Seirei Keiyaku), Rio is bonded with Aishia, a high-ranked universal-attribute spirit who resides within his soul. Their connection extends further through the Spirit Pact (Seirei Reiyaku), a secret technique that allows them to assimilate into a single being. This fusion remakes Rio’s body into that of a spirit and grants access to Spirit Arms, a weapon manifested from the bonded spirit’s soul.

As the Dragon King’s reincarnation, Rio also wields a Divine Authority known as Annihilation, an inherent transcendent ability granted by the world’s true god. This power enables him to erase or nullify anything he can fully perceive. He first invoked this ability in Volume 20 against the Great Spirit of Earth, erasing a massive construct of earth before it could cause destruction.

Martial Arts
From Haruto’s memories, Rio inherited knowledge of Ancient Martial Arts, which he combined with Spirit Arts to enhance his physical abilities. This allowed him to defeat skilled opponents, including assassins, early in his journey. During his time at the Beltrum Kingdom Royal Academy, Rio honed his combat techniques further, excelling in swordsmanship to the point of surpassing the Royal Guard Charles Arbor—an accomplishment unmatched by his peers.

By the age of 16, Rio was regarded as a master swordsman, impressing allies and rivals alike. In addition to his sword skills, he is proficient in unarmed combat, demonstrated when he halted Takahisa’s blade with his bare hand during a duel, an act that astonished onlookers such as Satsuki.

Celia Claire
Celia Claire plays an important role in Rio’s early life and is one of the few characters who understands him deeply. They first met when Rio was seven years old, shortly after he regained the memories of Amakawa Haruto. Celia was struck by his polite speech and demeanor, unusual for a child from the slums. Following Rio’s enrollment in the Royal Academy, Celia became his primary confidant, holding tea parties with him in her laboratory. Their teacher-student relationship gradually developed into a close friendship, with Rio assisting her in organizing her research materials and cleaning her workspace. Celia, who had grown up without close companions due to the pressures placed on her from childhood, found comfort in Rio’s presence, while Rio valued her companionship in an otherwise hostile environment.

Zen
Rio’s father, Zen, was an adventurer and former royal guard of the Karasuki Kingdom. Before Rio’s birth, Zen distinguished himself in the kingdom’s army through his skill in spirit and martial arts, eventually earning the title of “Samurai.” He died around the time of Rio’s birth, the result of betrayal by his companion Lucius. Zen’s death, and the subsequent murder of Rio’s mother Ayame, left Rio orphaned and shaped his early years in the slums.

Aishia
Aishia is Rio’s contract spirit, a rare and powerful universal-attribute entity who has been bonded with him since the awakening of Haruto’s memories. Initially dormant, Aishia communicated with Rio in brief moments of guidance before later manifesting in her humanoid form after he rescued Miharu, Aki, and Masato. She knows all of Rio’s thoughts, dreams, and regrets, and is wholly devoted to him. Aishia often addresses him as Haruto, insisting that his past and present selves are inseparable. Only after Rio begins to accept this truth does she call him by his current name. Their bond extends beyond companionship, forming the foundation of his strength through the Spirit Pact.

Miharu Ayase
Miharu Ayase was Amakawa Haruto’s childhood friend and first love in his previous life. As children, they promised to marry each other when they grew up, a vow that shaped their personal efforts and aspirations. Haruto later enrolled in the same high school Miharu attended, but their reunion was thwarted by a misunderstanding regarding her relationship with Takahisa. Haruto’s hesitation left him with lasting regret, compounded when Miharu was suddenly transported to another world. Haruto carried this unfulfilled promise until his death. As Rio, he eventually encounters Miharu again in Volume 4, though he struggles with guilt and self-doubt. Believing his quest for vengeance and the lives he has taken make him unworthy of happiness, he distances himself from her despite still caring deeply.

The name Rio (リオ) is written in katakana, making it phonetically ambiguous. It can be interpreted as derived from the Portuguese and Spanish word río, meaning “river,” symbolizing flow and continuity. Within the context of the story, it may also highlight Rio’s ability to adapt and move forward despite hardship.

His birth name in his previous life, Haruto (春人), combines haru (春), meaning “spring,” with to (人), meaning “person,” which can be translated as “spring person” or “one of spring.” The name evokes renewal and beginnings, which parallels his reincarnation into a new world.