Rio was born in the Beltrum Kingdom to immigrant parents from Yagumo. His father, Zen, died from betrayal by his adventuring companion Lucius shortly before or after Rio's birth. His mother, Ayame, raised him alone until Lucius murdered her when Rio was five. Witnessing her death, Rio was cast into the capital's slums, enduring two harsh years as part of a gang's slave group. There, he harbored intense hatred and swore revenge against his mother's killer. At age seven, Rio regained memories of his previous life as Haruto Amakawa, a Japanese university student who died in a bus accident. This merging created internal conflict. While retaining Rio's core identity and vengeful drive, he integrated Haruto's memories, knowledge, ethical perspectives, and skills—including Japanese fluency and proficiency in ancient martial arts. The fusion resulted in a mature mindset atypical for his age, presenting as calm, analytical, and strategically inclined. His childhood appearance featured rare black hair, uncommon outside Yagumo, and an androgynous face, marked by scars from slum life. Despite gaining Haruto's adult memories, he identified primarily as Rio, though the fusion created ongoing tension between his desire for vengeance and Haruto's pacifist morality. This duality manifested as emotional guardedness and a belief his vengeful purpose made him unworthy of deep relationships or happiness. Survival in the slums required adaptability. He utilized Haruto's knowledge pragmatically, though initially remaining illiterate in the Strahl region's languages. His inherited martial arts skills proved critical when he defeated an assassin sent after him, showcasing combat prowess beyond his years. This period ingrained a tendency to avoid attention through excessive humility, a defense against jealousy and noble prejudice. A pivotal shift occurred when he intervened in the kidnapping of Princess Flora Beltrum. This act led to his wrongful imprisonment and torture by knights seeking a scapegoat. Exonerated, he accepted enrollment at the Beltrum Royal Academy as a reward, viewing it as a path to strength and resources for revenge. There, facing systemic discrimination from noble peers due to his commoner status, he maintained academic excellence rivaling top students like Princess Christina. His only ally was instructor Celia Claire, who taught him literacy and provided refuge in her laboratory. This isolation reinforced his distrust of others and emotional reserve. His academy tenure ended abruptly when nobles falsely accused him of endangering Flora during a military exercise. Forced to flee as a fugitive, he journeyed east toward his parents' homeland, seeking roots and inner stability. This phase marked the beginning of his gradual reconciliation between Rio's and Haruto's identities, though his foundational traits—strategic thinking, protective loyalty toward rare trusted individuals like his adoptive sister Latifa, and moral aversion to unnecessary violence—persisted.