Naoya Nitta (新田巨也, Nitta Naoya) is a killer consultant currently working with his old classmate, Shunsuke Saruwatari, with the aim of helping Saruwatari make a name for himself in Fukuoka. He is a member of the Kokura Fried Wings baseball team (Ogura Fried Udons in the anime).
Nitta is a young man who wears silver-framed glasses, a deep blue jacket, necktie, pinstripe shirt, and white chino pants. He carries a small handgun concealed on his person at all times.
Nitta is intelligent and strategic. He is thoughtful toward his clients, thoroughly considering their wants and needs to devise a strategy for them to achieve their goals. He displays patience and honesty toward whoever he is talking to, even if it is an act for formalities. In actuality, however, Nitta is quite apathetic toward others and finds the world quite dull, which leads into his interest in Shunsuke Saruwatari - someone he considers to be out-of-the-mold and a person he wants to hang around for entertainment value. With the exception of Saruwatari, his killers are simply tools to him.
Nitta and Saruwatari were never very close, but they were batterymates in their high school baseball club. Nitta observed Saruwatari's anger and frustration after a game in which he tried to carry his whole team's weight on his skill alone and was defeated by the teamwork of their opponents. Nitta develops an interest in Saruwatari's selfish ambitions and they carry the weight of their team together from then on. One day they played together well but the game still ended in their loss, and Saruwatari, angered by the loss and Nitta's apparent indifference, punched him in the face. Two would not meet again until Satuwatari returned to Kokura seven years later. Sometime after high school, Nitta strayed from a normal lifestyle and applied his social skills and business instincts into becoming a consultant for hitmen in Fukuoka.
More recently, as a killer consultant, Nitta offered his services to George Gondo. He advised him to pose as the infamous killer known as G.G. in order to quickly earn the huge sums of money needed to pay for Gondo's daughter's medical treatment.
Niwaka Samurai Impersonator Arc
Nitta encounters his old acquaintance, Saruwatari, not long after he arrives in Kyushu. Although Saruwatari does not immediately recognize him, they head out together to eat and catch up. Nitta reveals that he is a killer consultant and offers his services to Saruwatari, promising to make him the number one killer in Fukuoka.
The next time they meet up in Lady Madonna, Nitta begins to offer advice to Saruwatari about how he can make a name for himself, namely, by choosing a signature weapon. He specifically recommends ninja-like weapons, urging a reluctant Saruwatari to practice throwing shurikens.
Some time later, Nitta gives Saruwatari the task of hunting down two or three killers, giving him a list of killers operating in the city of Kitakyushu. He is shocked, however, when he calls Saruwatari to find out that he has killed all but one. Nevertheless, Nitta assures him that this is a good thing, since having an eyewitness will mean that rumors of Saruwatari will start spreading.
Later, Nitta asks Saruwatari if he will participate in tryouts for the Kakyuu Association. He does so and lets a shocked Nitta know that he has been given the job of killing the Niwaka Samurai. Nitta immediately searches for any information regarding the Niwaka Samurai and, on Undergroundjobs.com, finds a listing that has apparently been made by the Niwaka Samurai, who is looking for jobs to take on. He immediately suspects it to be fake. Even though Saruwatari agrees and knows it is a waste of time, he decides to contact them anyway.
After Saruwatari loses the second Niwaka Samurai and his money to Abe and Yamamoto, he has Nitta come to Hakata and meet him in Tully's Coffee on the ground floor of the Gate's building. Nitta helps track them down by using the tracking device Saruwatari placed on their van. After locating them, Nitta accompanies Saruwatari in confronting Abe and Yamamoto and taking back the stolen money. They discover the body of the supposed Niwaka Samurai, and upon finding out that this one is also a fake, Nitta presses the pair for information about the Niwaka Samurai's mediator and decides to use the fake Niwaka Samurai as bait to lure out the real one.
The next morning, after Saruwatari's first battle with the real Niwaka Samurai, Nitta meets up with Sayuri, who had called for him to meet her at the Grand Hyatt Fukuoka, the hotel attached to Canal City. She has just finished her job of killing Long Fang Wang, and Nitta aids her escape by giving her a hotel employee uniform. He goes on to ask Sayuri if she will carry out a request he has received from a woman in prison, but she declines. It is not long before he decides to contact George Gondo, who accepts the job to kill Saitoh.
Later, Nitta calls Saruwatari after worrying that he had been killed by the Niwaka Samurai, and at some point Gondo informs him that a killer from Murder, Inc. who had also been pursuing Saitoh beat him to the job.
Shou Wang Arc
As Nitta is racing to a meeting with a client, he questions Saruwatari on his relationship with Zenji Banba. Saruwatari demands he stop the car so he can practice pitching at a batting center, leaving Nitta to go to work alone.
Nitta meets with Tony Lau, a Shou Wang executive, in Ohori Park. The pair rent a paddleboat so they can talk privately, and Tony hands Nitta two files on Kakyuu Group executives, offering him an employment examination for Saruwatari. Before paddling to shore, Nitta is questioned on his relationship with Saruwatari and reassures Tony that his killers are only tools. To help Saruwatari complete Tony's employment exam, Nitta drives Saruwatari to Byeong-Hee Kim's apartment and Takashi Unoyama's office.
Days later, Nitta meets Saruwatari in the basement of Lady Madonna to ask about Kubota's assassination, and he instructs Saruwatari to wait in a hotel in Fukuoka city. Nitta forwards a distress call to him soon after, sending Saruwatari to Shou Wang's warehouse on the pier, where syndicate members have been attacked by a hitman. When Nitta arrives at the pier, Saruwatari has emerged from the water, soaking wet. He comments on Saruwatari's inability to swim and is punched in the gut in return. Tony Lau meets them at the warehouse, and just after his arrival, one of the missing Shou Wang members reappears with the head of his comrade in a box.
Nitta meets with Tony at Ohori Park later, where they rent a paddleboat and paddle to the center of the lake. Tony informs Nitta of Shou Wang's truce with the Kakyuu Group and their deal to exchange killers. He gives Nitta a bag with a powdered sleeping drug in it to give to Saruwatari. Afterward, Nitta verifies that it is a sleeping drug and invites Saruwatari to lunch.
The next day, the pair eat together, and Nitta doses Saruwatari's cola while the killer is in the restroom. Saruwatari passes out minutes later, and Nitta carries him to the car. He greets Saruwatari when he awakens, bound to a chair in Shou Wang's warehouse. Nitta calmly explains the situation to him. Tony hands Nitta 50,000,000 yen in a briefcase, and the consultant gives Saruwatari a gentle farewell hug from behind and steps away. When Tony raises his gun to shoot Saruwatari, Nitta shoots him in the hand with his handgun and releases Saruwatari, who immediately punches Nitta in the face.
After apologizing to Saruwatari, Nitta explains to Tony why he saved Saruwatari. Even more angered at being called a tool, Saruwatari kills Tony and checks the briefcase. Nitta pleads with a furious Saruwatari to believe that he has not betrayed him, and eventually accepts 15.2% of the money.
Nitta drives Saruwatari to the front gate of the Kakyuu Association's headquarters immediately afterward, where the killer intends to settle the score with Zhao, and is taken aback when Saruwatari rings the bell. He watches Saruwatari provoke the mafia, and when several dozen armed men appear at the front gate, the consultant leaps back in his car and flees.
Nitta presents Saruwatari with an interesting job: killing a hitman in Fukuoka. When Saruwatari calls him later after meeting the client, furious that his target is not the Niwaka Samurai, Nitta feigns ignorance and laughs.
- Nitta gave Saruwatari the nickname "Sarucchi" because he tuts ("chi") a lot.