Nu is a wolf-form servant to the Genma Consul, the Maoh King. His primary mission is monitoring and protecting Jin, one of the twin sons born to the human woman Non and the Maoh King, following Jin's birth and upbringing in a human village under Non's care.

Throughout Jin's childhood, Nu acts as a guardian and parental figure, offering protective stability against villagers ostracizing the boy for his demonic heritage. Nu witnesses Jin's latent Genma powers awaken traumatically when Genma soldiers assault and kill Non, revealing Jin's destructive potential and profound emotional turmoil.

Nu maintains respectful support for Non, acknowledging her sacrifices and hardships. His loyalty extends beyond duty to the Maoh King, showing genuine concern for Non and Jin's well-being. This connection ends when resistance leader Dan strikes Nu a mortal blow during an encounter. Nu's death becomes a catalyst for Jin's intensified rage and vengeance, leading directly to Dan's execution.

Nu's character arc concludes with his death, leaving a lasting impact on Jin's motivations and emotional path. His role as protector and his connection to Jin's formative experiences bridge the boy's human upbringing and demonic lineage, underscoring Nu's narrative significance.