In her human form, Blue appears as an olive-skinned woman with sharp blue eyes, tousled black hair, and striking red lips. She wears a long, dark coat fastened with silver buttons, cinched at the waist with a belt and extending to her mid-thighs. A red scarf is loosely tied around her neck, with one end draped over her chest. Her outfit is completed with thigh-high black boots featuring low heels.

In her true form, Blue is a wolf-dog hybrid with dark blue fur, reflecting her name. Her appearance leans more toward that of a wolf, though she is slightly slimmer in build. She has piercing blue eyes reminiscent of huskies and is first seen wearing a silver spiked collar, emphasizing her past as a domesticated animal.

Blue shares a strong attachment to humans, much like Toboe, due to having lived among them her entire life. She was deeply loyal to Quent Yaiden, faithfully following his commands without question. However, after her encounter with Cheza awakened her latent wolf heritage, Blue began to feel more connected to her true nature and ultimately chose to follow that path.

Unlike Quent, whose actions were often impulsive and emotionally driven, Blue displayed a calm and rational demeanor. Though typically composed and reserved, she was fiercely protective of those she cared about and could become quickly enraged when they were threatened.

Little is known about Blue’s early origins, including her birth name, parentage, or where she came from. As a pup, she was apparently abandoned but later discovered by Ruus Yaiden, the son of Quent Yaiden. Blue was raised in the town of Kyrios by Ruus and his family until the town was engulfed in flames and destroyed.

During the catastrophe, Blue and Quent survived, but Ruus and Quent’s wife were killed in the fire. In the aftermath, Blue and Quent witnessed a pack of wolves emerging from the burning town, seemingly feeding on the remains of the fallen. Quent came to believe that wolves were responsible for the destruction, which fueled his hatred and obsession. However, the wolves were likely drawn to the scene by the chaos caused by Lady Jaguara’s soldiers, who were targeting wolves at the time.

This truth only came to light later, when Blue overheard soldiers in Jaguara’s fortress discussing the incident. Despite Blue’s revelation to Quent that she was part wolf and could take human form, he struggled to accept the truth, remaining bound to his long-standing belief in the wolves’ guilt.

Blue is introduced as Quent Yaiden’s loyal companion, aiding him in his mission to hunt down wolves, whom he blames for the destruction of their hometown, Kyrios. While tracking a white wolf, the pair arrives in Freeze City, where Blue begins to sense the presence of wolves disguised as humans. Her instincts become sharper after an encounter with Tsume, a gray wolf, whom she injures but fails to capture.

As their search continues, Blue’s suspicions grow stronger. She is injured during a confrontation with Tsume, and while recovering, she begins to question her purpose. Eventually, she senses Cheza, the Flower Maiden, whose presence awakens Blue’s dormant wolf blood. Though shocked by this revelation, Blue becomes aware of her true nature and is unable to continue hunting her kind.

Afterward, Blue saves a young boy from being harmed by soldiers but is misjudged by Quent, who begins to doubt her loyalty. When she is later beaten and shot by a soldier, Blue escapes and goes missing. Quent finds her gravely wounded but leaves to pursue the wolves, promising to return. Upon his return, Blue has vanished.

Struggling with her identity and uncertain about her place in the world, Blue begins a solitary journey. She eventually discovers her ability to take on a human guise and narrowly escapes danger at a black market before reuniting with Kiba’s pack. After they save her, Hige invites her to join them, but she initially declines.

Later, Blue reunites with Quent in Lady Jaguara’s city. Disguised as a human, she cares for him while he is unconscious and reveals the truth behind Kyrios’ destruction that it was caused by Jaguara’s soldiers, not wolves. Though Quent initially rejects the truth, Blue emotionally appeals to him, calling him “Pops,” which prompts him to recognize her and embrace her. Despite the reconciliation, Blue affirms that she is no longer his dog, marking a shift in her identity and loyalties.

• Quent Yaiden: Blue viewed Quent Yaiden and his family particularly his son Ruus as her own, forming a deep emotional bond with them during her time in Kyrios. She regarded Quent as a father figure and remained fiercely loyal to him, dedicated to his safety and approval. Their relationship was rooted in mutual trust, although Quent continued to see her as his pet. Upon awakening to her wolf heritage, Blue struggled with the conflict between her loyalty to Quent and her new identity. She ultimately chose to stop hunting wolves, placing a strain on their bond. Despite this, Blue’s care for Quent never diminished. She risked revealing painful truths to him, including the real cause behind Kyrios’ destruction and her desire to follow the wolves to Paradise. Their relationship finds closure when Quent, in his final moments, acknowledges her as “his dog,” bringing peace to Blue and healing the rift between them.

• Hige: Blue and Hige are the only two members of the pack to form a romantic relationship. Initially skeptical of Hige’s laid-back attitude, Blue gradually opens up to him, and the two develop a close emotional bond. Their connection deepens as they travel together, with Blue expressing her commitment to remain by his side regardless of whether Paradise will accept her as a half-wolf. In the final act of their journey, the two die together in each other’s arms after their confrontation with Lord Darcia III, underscoring the strength of their love and loyalty.

Blue’s name is written in katakana as ブルー (Burū), the transliteration of the English word “blue.” The name reflects both her appearance and deeper symbolic traits. In her wolf form, Blue has dark blue fur and piercing blue eyes, which visually support her name. The color blue also often symbolizes calmness, loyalty, and inner strength qualities that align with her composed attitude, strong sense of loyalty, and emotional resilience throughout the series.