Eruru is a central female character whose actions set the story of Utawarerumono into motion. She is a young woman belonging to a race of people characterized by animal-like ears and tails, typically depicted with wolf-like features including large brown eyes, pale skin, and dark grey hair she often wears in a low ponytail. Her name is derived from a fictional flower that exists only within the world of the narrative.

Eruru lives in the small village of Yamayura with her younger sister Aruruu and their grandmother Tusukuru. Her life changes forever when she discovers a masked, amnesiac man severely wounded in the forest and nurses him back to health. This man, who later takes the name Hakuoro, becomes the central figure of the story, and Eruru acts as his primary caretaker, guide, and eventual confidante.

In terms of personality, Eruru has a forceful but caring nature. She is described as strong-willed and empathetic, putting all her heart and effort into everything she does. While she is generally kind, cheerful, and beloved by her fellow villagers, she also has a jealous streak and can be quite expressive with her displeasure. She takes on a maternal and protective role towards her younger sister Aruruu, frequently scolding her out of genuine concern for her safety. Behind her outward strength, she tends to conceal her own painful feelings, particularly regarding the loss of her grandmother and her growing romantic affection for Hakuoro, in an effort to keep those around her happy.

Her primary role in the story is that of a healer and a steadfast supporter. As an apprentice healer trained by her grandmother, she is responsible for tending to the wounded and sick. She becomes Hakuoro's personal servant after he rises to a position of leadership, remaining a constant presence by his side through numerous battles and political struggles.

Eruru's key relationships define her character arc. Her bond with Hakuoro evolves from patient and caretaker to deep romantic love, partly inspired by observing how kindly he treats her sister Aruruu and how he fills a paternal void in the younger girl's life. Her relationship with Aruruu is central to her identity; she is fiercely protective of her sister and worries about her constantly. She also shares a deep bond with her grandmother Tusukuru, who serves as her teacher in the healing arts. Later in the timeline, it is revealed that Eruru helps raise the child Kuon, suggesting she may be the closest to Kuon among all her maternal figures and likely teaches her the healing arts and a traditional song she once used for Hakuoro.

Throughout the series, Eruru's character develops from a village girl into a woman of great emotional resilience. She learns to confront her feelings rather than hide them entirely, culminating in her confession of love to Hakuoro at the story's climax. She demonstrates profound patience and devotion, spending many years watching over Hakuoro's seal as a shrine caretaker while waiting for his promised return. Her notable abilities lie almost entirely in the field of medicine. As a skilled practitioner and healer, she is adept at creating remedies and treating injuries. Her talents in this area are so significant that she is able to nurse Hakuoro back from the brink of death and continues to serve as a vital healer throughout the conflicts that follow.