Nero Yuzurizaki is a 15-year-old female detective and core Milky Holmes member. Originally a detective from Britain during the Great Detective Era, she wields supernatural powers called Toys, like others in that time. Her name references the literary detective Nero Wolfe. She stands 152 cm tall, weighs 42 kg, has green eyes, and short orange hair often styled with spiky bangs or twin tails. Her typical ouji-style uniform includes shorts, a cape, knee-high socks, and a flat cap, emphasizing a tomboyish look.

Nero presents a rough, selfish exterior, frequently using the masculine pronoun "boku." She displays greed, often prioritizing her own needs—especially her substantial appetite—while talking down to others. Despite this, she possesses a fiercely loyal and protective core, consistently supporting and safeguarding her Milky Holmes teammates in crises. This duality leads her to employ underhanded tactics, which become strategically vital after the team loses their Toys. Her primary Toy allows control of machines via a small metal fragment. This power extends beyond manipulation; she can disassemble machinery and reconstruct, enhance, or radically transform devices using surrounding materials. The full scope remains ambiguous, making her powers the least defined in the team. This skill is also classified broadly as Technology Manipulation or Mechanical Manipulation, enabling interface with both electronic systems and purely mechanical objects.

Her story unfolds across all media, tied to the team's journey. In the main anime, she and Milky Holmes suffer a pivotal defeat against the Gentlemen Thieves, resulting in permanent Toy loss. This forces them into harsh living conditions in their academy's attic, intensifying her reliance on cunning. During this time, her relationships deepen, notably with teammate Cordelia Glauca, evidenced by shared sleeping arrangements and physical affection like cheek-licking. She also harbors a romantic interest in Hercule Barton. Subsequent arcs, including agricultural endeavors and battles against antagonists like the Colors the Phantom group, showcase her adaptability. Her resilience peaks in the franchise finale during a climactic space battle against Arsène, demonstrating unwavering commitment to her team. This narrative spans all seasons, OVAs, movies, and the special episode "Psycho's Greeting," showing her growth from a self-centered individual to a dedicated protector.