Keyaru is initially portrayed as a gentle and optimistic boy with aspirations of becoming a hero. Upon learning that he had been chosen as the Hero of Healing, he expressed excitement but also fear, as his ability to heal transferred both the pain and memories of those he aided onto himself. His compassionate and naïve nature, however, left him vulnerable to exploitation.

After enduring years of imprisonment, torture, and abuse at the hands of his supposed allies, Keyaru’s personality underwent a drastic transformation. Once released and given the chance to alter the past, he abandoned his former kindness and adopted a vindictive, cruel, and calculating disposition. He became sadistic and relentless, deriving satisfaction from enacting revenge on those who wronged him. His outlook on morality shifted into a warped framework defined entirely by personal vengeance and self-preservation, often leading him to replicate the same cruelty inflicted upon him.

Revenge serves as Keyaru’s driving motivation, with his actions guided by a belief that his abusers must not be allowed to live without consequence. He takes explicit pleasure in the suffering of his enemies, often displaying manic satisfaction during acts of vengeance. Despite this, Keyaru has also demonstrated exceptions to his cruelty; he distinguishes between those who wronged him and those uninvolved, generally avoiding harm to innocents. He has also shown empathy toward individuals seeking revenge for their own suffering, occasionally aiding them if their goals align with his.

Keyaru’s relationships with his companions are complex. Outwardly, he treats party members such as Freia, Setsuna, and others with kindness, in stark contrast to the abuse he once suffered. However, his internal thoughts often refer to them as “toys” or tools, suggesting a lack of genuine emotional attachment. At the same time, he has displayed anger and protectiveness when they are threatened or harmed, indicating an ambiguous mix of possessiveness and possibly suppressed care. He has admitted that at times his thirst for revenge momentarily diminishes while traveling with them, though he consciously suppresses these feelings to maintain focus on his larger mission.

Overall, Keyaru is depicted as a character consumed by vengeance, exhibiting traits of cruelty, cunning, and instability, while still bound by selective principles that prevent indiscriminate violence. His moral ambiguity, combined with moments of unexpected kindness, underscores his complexity as both an anti-hero and a perpetrator of brutality.

Keyaru is depicted as a young man of medium height with brown hair and red eyes. Before becoming the Hero of Healing, he is shown wearing simple village clothing. Following the beginning of his revenge, he acquires and wears a set of armor stolen from the Captain of the Guards. When using his healing ability, his eyes temporarily turn green, marking the activation of his power.

After altering the past, he adopts the identity of Keyaruga, which is visually presented as an older version of himself, maintaining the same core features with a more mature appearance. He also assumes the disguise of Keara, a female persona used for infiltration. In this form, he takes on the appearance of a buxom maiden with waist-length brown hair tied with a red ribbon, while his biological sex remains unchanged.

Keyaru was born in a small rural village within the Jioral Kingdom. From an early age, he was known for his gentle disposition and optimism, qualities that set him apart from many of his peers. On his fourteenth birthday, he was chosen as the Hero of Healing, one of the four legendary Heroes tasked with protecting the world. Although this designation initially filled him with excitement, he soon discovered the burden of his gift: his healing ability not only repaired injuries but also transferred the physical pain and memories of those he healed into himself.

His inability to cope with this side effect made him vulnerable to manipulation. Keyaru was quickly betrayed by those around him, particularly members of the royal court and fellow Heroes. He was imprisoned, drugged, and subjected to repeated abuse and torture, ensuring he remained compliant while his powers were exploited to enhance others. This cycle of cruelty continued for years, leaving him broken and resentful.

Eventually, Keyaru obtained the Philosopher’s Stone, an artifact capable of granting immense power. Using it, he rewound time by four years, returning to the period just before his suffering began. Determined to change his fate, he adopted the new identity of Keyaruga and began a calculated campaign of vengeance against those who had wronged him. His quest for retribution ultimately led him to assassinate the king of Jioral and seize the throne, vowing to reshape the kingdom into a realm of peace—albeit through methods born of violence and manipulation.

Anna
Anna was Keyaru’s childhood friend and first love. The two grew up together in Alban village, with Anna treating him as both a younger brother and a close companion. Following the death of his parents, Anna supported him emotionally, often visiting and offering him a place with her family. In the light novel and manga, Anna is raped by Renard and, mistaking him for Keyaru, commits suicide. In the anime adaptation, however, she survives long enough to see the real Keyaru before dying with a smile. Her fate deeply scars Keyaru and fuels his quest for vengeance. His retribution against the Knight Captain reflects this trauma, and he continues to refer to Anna as his first love, mourning her loss throughout his journey.

Flare / Freia
Flare, the first princess of Jioral, exploited Keyaru’s healing powers, subjecting him to prolonged abuse. She played a central role in breaking his spirit and was the initial catalyst for his transformation into Keyaruga. She became his first target of revenge: after gaining enough power, he raped her, erased her memories, altered her appearance, and enslaved her under the new identity of Freia. As Freia, she shows none of Flare’s cruelty and instead becomes loyal, affectionate, and protective of Keyaru, though he continues to refer to her as a “toy.” Despite this, their relationship evolves into a complicated dynamic: he both uses her as a tool of vengeance and shows moments of genuine care, often defending her in battle while questioning whether her former malevolence was the product of her upbringing in Jioral.

Setsuna
Setsuna, a demi-human warrior, earns Keyaru’s trust through her determination and raw combat ability. He aids her in overcoming her limitations by enhancing her growth with his abilities, valuing her as a reliable ally in close combat. Setsuna frequently protects Freia and Ellen from direct attacks, and her loyalty to Keyaru becomes evident through her willingness to fight at his side. Though their bond grows closer and occasionally intimate, Setsuna often shows jealousy toward Freia and other women in his company, creating a competitive tension within the group.

Kureha Clyret
Initially, Kureha meets Keyaru as an enemy, but after her arm is restored through his powers, she expresses gratitude and vows to repay him. Their paths cross again after his escape, leading to a duel in which she is defeated. Learning the truth about the corruption of the Jioral Kingdom, she joins him as an ally. Respectful of demi-humans and motivated by her sense of justice, she is among the few individuals from Keyaru’s past toward whom he harbors no hatred. Under the influence of an aphrodisiac used during battle, Kureha develops a romantic infatuation with him, an attachment that persists even after she inherits the title of Sword Hero following Blade’s death.

Eve Reese
Eve Reese, a future Demon King, first encounters Keyaru after he rewinds time. He rescues her from attackers in a tavern in Buranikka, swearing to support her rise to power in order to foster coexistence between humans and demons. Their alliance grows into a personal relationship, and during their quest to claim the power of the divine bird Caladrius, they develop a romantic bond. Eve becomes both a trusted partner and one of Keyaru’s lovers, representing his more pragmatic yet idealistic ambition of reshaping the world.

Keyaru’s names draw inspiration from healing magic terminology in the Final Fantasy video game series. His birth name Keyaru (ケヤル) resembles Cure, the basic healing spell; his assumed identity Keyaruga (ケヤルガ) parallels Curaga, an advanced form of the spell; and his female disguise Keara (ケアーラ) corresponds to Cura, an intermediate variant. This naming convention reinforces his role as the Hero of Healing. In contrast, the character Flare bears a name associated with offensive magic, highlighting the thematic opposition between restoration and destruction.