Nate Mitotsudaira is a student from Hexagone Française attending Musashi Ariadust Academy, where she serves as the Fifth Special Agent of the Chancellor Board, a position focused on field operations. She is a half-human, half-werewolf, born to a pure-blooded werewolf mother and a human father. As a result of her mixed heritage, she cannot transform into a full wolf form, but she possesses immense physical strength and heightened regenerative abilities that are always active. She is the recognized successor of the Mitotsudaira Clan and also holds the title of branch successor to the Matsudaira name, making her the only active-duty knight on the Musashi during the events of the story, as the other knights are either too young, inexperienced, or have been forced out by age restrictions.

Nate is defined by a chivalrous nature and a strong sense of duty. She is deeply protective of the land of the Musashi, which technically falls within her family's domain, and she takes her role as a knight seriously. She holds Toori Aoi in high regard, viewing him as her king and following him with unwavering loyalty. She has also developed romantic feelings for him, which she is aware of. She is earnest and straightforward in her devotion, though she can be vulnerable to improvisation and citrus fruits, which are noted weaknesses for her. Her sense of justice and noble status are rooted in her upbringing and her position as a high-ranking successor; her inheritance rank within the Far East is second only to Horizon herself, meaning she was designated to become the new ruler of the Far East had Horizon been executed.

In the story, Nate acts as a frontline combatant and protector for the Musashi and its chancellor council. She participates directly in the conflicts that arise during the journey, including the engagements with Tres España and the events in the floating nation of England. Her motivations are driven by her knightly code, her loyalty to Toori, and her desire to safeguard the people and territory under her family's protection.

Nate wields a special weapon known as the silver chains, which are divine armaments that can follow her mental commands and also possess an independent consciousness capable of defending her autonomously. The chains can express simple emotions by shaping themselves into letters or forms. In combat, she uses the chains to augment her already formidable physical strength, allowing her to throw large objects or restrain opponents with great force. Her appearance includes very long silver hair styled into five large drill-shaped curls in the back and two smaller ones that hang in front of her shoulders, and her nickname within the story is the Silver Wolf, or Argente Loup.