Nonoha Itou grew up alongside Kaito Daimon and has been his closest friend since childhood. She remained by his side following the death of his parents, often taking on a caretaker role by ensuring he eats properly, attends school, and avoids isolating himself in puzzles. Her strong bond with Kaito gives her an intuitive understanding of his feelings and motivations, even when he does not express them directly.

Unlike most of the central cast, Nonoha is not a natural puzzle solver and initially shows little interest in them. However, her determination to support Kaito leads her to engage with puzzles despite her lack of talent, demonstrating her loyalty and perseverance. Over time, she is recognized for her dedication and receives the title of “Nightingale,” reflecting her role as a supporter and healer within the group rather than a direct solver.

Nonoha Itou has medium-length brown hair, which she typically ties into a distinctive split ponytail, and layered brown eyes. Her appearance is often described as cheerful and approachable, complementing her lively personality.

In the beginning of the series, she wears the standard school uniform: a white shirt with a red ribbon tied at the collar, a purple skirt that extends slightly past her knees, and pink sneakers. Outside of school, her clothing choices are casual and colorful. For example, when accompanying Kaito Daimon to the Sage Puzzle on Minotaur’s invitation, she is seen in a pink sweater layered over a darker pink shirt with maroon shorts.

Although Nonoha Itou lacks talent in puzzle solving, she compensates with strong athletic ability and a photographic memory, making her an invaluable supporter to Kaito Daimon and his team. More than anyone else, she shows deep concern for Kaito’s well-being, often prioritizing his safety over her own.

Nonoha is portrayed as headstrong and determined, unafraid to pursue what she believes is right. Her physical strength is also a recurring comedic trait; she has been shown kicking Kaito into the air or restraining him in a headlock when frustrated. At the same time, her impulsive and reckless side often surfaces, as seen when she ignored Kaito’s warnings and recklessly explored the Sage Puzzle despite knowing it was a dangerous labyrinth.

Nonoha Itou first appears expressing frustration that her best friend Kaito Daimon left without eating the breakfast she had prepared. At school, she discovers that Kaito has built a puzzle out of classroom desks. Annoyed, she confronts him, kicking him into the air before putting him in a headlock to demand he return the desks.

Later, she accompanies Kaito to the Puzzle Club, despite warning him that it would only lead to trouble. There, she observes his remarkable speed in solving a sudoku puzzle and is surprised by his ability. When the club president, Souji Jikukawa, mentions an invitation from “Minotaur” to attempt the dangerous Sage Puzzle, Nonoha reluctantly follows Kaito into the ruins after he insists on going.

Inside the labyrinth, Nonoha attempts to guide their way by keeping her hand on the wall, a method she had read about online. This recklessness nearly costs her when she falls through a trap door, but Kaito manages to save her. Despite his protests, she continues to help, using her sharp memory to retrace their steps when Kaito becomes disoriented. She also notices details in the puzzle’s construction that allow Kaito to progress further, demonstrating her usefulness despite not being a solver herself.

At the puzzle’s climax, Kaito is forced to face the challenge alone while Nonoha anxiously tries to break through a locked door to reach him. As the labyrinth begins to collapse, she desperately calls out his name, underscoring her determination to protect him even when she cannot directly assist with the puzzle itself.

The name Nonoha is a pun referencing the puzzle game “Tower of Hanoi” (hanoi no tō in Japanese), which is an anagram of Itō Nonoha. Her surname, Itō (井藤), combines i (井), meaning “well,” “mine shaft,” or “pit,” and tō (藤), meaning “wisteria.”