Nonoha Itou (井藤ノノハItō Nonoha) is the female protagonist of Phi Brain: Kami no Puzzle. She is Kaito Daimon's best friend and current partner. She also holds the title Nightingale.
In the beginning, she is seen in the standard school uniform, a white t-shirt with a red ribbon tied into the collar and purple skirt that went a little over her knees and pink sneakers.
She is always seen with her brown hair up in a split ponytail and her eyes are a layered brown.When going to the Sage Puzzle by invitation of "Minotaur" with Kaito she is seen wearing a pink sweater overlapping a darker pink shirt with maroon shorts.
Nonoha seems very headstrong, going for what she believes in, she also seems very strong, being able to kick Kaito Daimon straight up into the air, then putting him in a headlock. She's also reckless, not listen to Kaito when he tells her to stop running around the Sage Puzzle even when she had heard earlier that it was a deadly lybrinth.
Nonoha is seen first complaining about how her best friend, Kaito Daimon, left before her even when she had made breakfast and went to pick him up. She walks into the school yard, seeing the puzzle Kaito had made out of desks and wonders what's going on.
She is then seen running up to Kaito and kicking up in the air and onto the ground, grabbing him in a headlock, demanding that he return the desks - he quickly complies.
Her and Kaito are walking down the one of the school's hallways, going to the Puzzle Club - which Nonoha tries fruitlessly to talk Kaito out of, saying that he'll only get into a fight. They go to the club anyway and she seems suspicious of anything in the club. When they sit in the waiting room Takeda walks in offering a sudoku, which Nonoha asks what it was. When Takeda explains and hands the paper over to Kaito, she watches him and was amazed at the speed he was able to finish it in. She looks up as the president Souji Jikukawa walks in and welcomes them to the Puzzle Club, asking if Kaito would like to join, which he immediately declines. He asks instead, what the gadget Souji had given him last night was.
Nonoha watched as Kaito explained what had happened with invititation from "Minotaur". She had asked if he was the high-schooler that had saved the "Puzzle King". Kaito agreed, but stated that the Okudera was nothing more than a third-rate puzzler. She watched as Souji used Kaito's pride as a puzzler to get him to agree in going through the Sage Puzzle ruins that a message from "Minotaur" asks him to.
They're seen again walking through the forest to get to the Sage Puzzle ruins. Nonoha asked if Kaito was really going to do this, he says yes. She tries to talk him out of it, only to get him to tell her she needs to go home. She asked why he was so determined. He told her it was a promise. Kaito begins to walk in, Nonoha following, saying that she needed to keep an eye on him, and that she could protect herself.
Kaito told her to do what she liked. "Minotaur" appeared on a rock ledge, greeting Kaito. "Minotaur" explains that the Sage Puzzle is a barrier, and inside that barrier is a great treasure. Those who go through the puzzle, wins. Those who can't, face a great misfortune. Kaito only wanted to solve the unsolvable puzzle. Nonoha asked what they were going to do and they ran into the puzzle.
Kaito explained to her that they were at the entrance and he wanted to go to a certain dead end near the middle when Nonoha asked what they were going to do when he said earlier that it was unsolvable. Nonoha smiled, said that she would handle it and darted off, her left hand grazing the wall. She read on the net that if she kept her hand on the wall they would always find the exit. Kaito didn't believe it.
A trapped door opened up below her feet, forcing her downward. She flailed, trying to reach the edge, but couldn't. Kaito jumped over the edge and forced his arm to grab hers, while flipping over the trap door. He caught her and pulled her back up.
They walked back, trying to backtrack their steps, but Kaito couldn't remember. Nonoha did, so she led them back, Kaito trying to keep her from getting lost again.
They reach the dead end that Kaito wanted to see, but couldn't find any way to get through. Nonoha noticed that the corner looked different in the fact that the rails were behind the support beams instead of the other way around like the rest of the puzzle. Kaito wanted to know if she had seen an axe insignia anywhere. She pointed to a nearby corner support. Kaito walked up to it and examines it before pulling it out. The wall Kaito was examining earlier began to pull back and slide before revealing a new route. Nonoha was surprised.
They reached the end when they opened the final doors, revealling a temple atop a long staircase that "Minotaur" stated that Kaito had to go up alone. Nonoha yelled after that she didn't care what happened to him.
She got concerned when Kaito fell backwards out of the temple, yelling. She heard that Kaito had to solve a complex puzzle with his new power or they would die. When she heard that, she began to pull at the door that had closed earlier, telling it to open. When water and cannals began to collapse near her, she began to try to kick the door open. When the puzzle began to collapse even more, she called Kaito's name.
- She has a photographic memory.
- Nonoha's name is a pun on the game "Tower of Hanoi" ("hanoi no tou" in Japanese which is an anagram of "Itou Nonoha")