|Anime||Round 25 (New Challenger)|
|Family|| Itagaki's Father (Father)|
Itagaki's Mother (Mother)
Itagaki Manabu (Brother)
|Voice Actor||Kobayashi Yuu|
She is the the younger sister of Itagaki Manabu, who attends his boxing to cheering him on. Nanako is also romantically interested in Makunouchi Ippo, and hugs him when ever she see him. She tries to come between Mashiba Kumi and Ippo when ever she sees them together.
After Itagaki won his 2nd match, he invited Ippo to his home to meet his family and celebrate his win. When he arrives, he notices how poor the house is. When Nanako see Ippo, she hugs him and Itagaki introduces her and mentions that she is a big fan of his. Itagaki then introduces his mother.
After Itagaki's Father arrives, dinner is about to begin, but they say "Itagakimasu". During dinner, they continue to make pun, which makes it hard for Ippo not to laugh. They continue to make jokes and Ippo tries to join them with a pun.
Prior to Ippo's match with Shimabukuro Iwao, when Ippo reached peak physical exhaustion, Kamogawa told Ippo that he is not to practice or work out for a full week. He mentions if Ippo wants to do something, he can only soak in a pool. Aoki mentions he will get someone to keep an eye on him. In the local swimming pool, Kumi catches Ippo trying to work out and stops him since Aoki told Kumi that Ippo isn't suppose to do anything but rest. Itagaki and Nanako show up too, where Kumi starts to get mad at Nanako when she mentions her age. Nanako mentions that she hasn't heard Ippo has a girlfriend, which makes Kumi wonder what her relationship with Ippo is.
Kumi and Nanako talk about their brother being boxers. Kumi doesn't like to go to the match since they scare her, but Nanako does since she thinks fighting men are all cool. Kumi is a little jealous of her positive attitude on it. Nanako mentions she is jealous of Ippo and Kumi's relationship. When Kumi ask "What relationship?" Nanako thinks there is a little space available or she has a chance if she works hard. While they are talking, Ippo thinks that female friendships is a beautiful thing. After Ippo is done, he goes out to eat with Kumi.
After the match, Nanako visits Ippo, and learns he has been sleeping the last two days. Ippo's mother tells her it is okay to check in on him while he is sleeping. Kumi visits a little later, and catches Nanako trying to kiss Ippo while he is a sleep. Kumi mentions she is here to take care of Ippo since she is a nurse.
While she is fighting with Nanako, Iimura Mari enters Ippo's room and criticises them for being too noisy. Mari is stopping by in order to interview Ippo, but won't happen while he is still out. Instead, she search thru Ippo's bedroom, looking through his photo albums with Nanako. Kumi doesn't want to look without Ippo's permission. Kumi wonders if Mari is also interested in Ippo too.
Mari notes based on how Kumi and Nanako are acting, they never made it far in their relationship with Ippo if they never been in his bedroom before. Mari mentions that she is interested in Ippo, which shocks Nanako and Kumi. Kumi tries to get them to leave in order for her to take care of Ippo since she is a nurse, which cause tem to start fighting with each other. Ippo's mother enters with some tea for them. She mentions that when Ippo is like this, she tries to let him sleep as peacefully as she can, which makes Nanako, Mari, and Kumi feel guilty, and they decide to leave.
After Takamura's match against David Eagle , Kumi is helping Ippo and Itagaki train by timing their sprints. Itagaki wonders if Ippo is free this Saturday. Ippo, Kumi, and Itagaki Nanako mention they are free. Nanako thinks that was a close one, where she can't let her guard down with Kumi. Ippo tries to disagree, but tries to change the subject. Kumi thinks Itagaki is really into training, and mentions that he can win the Rookie King if he wins two more matches. Nanako mentions her brother is going to win, unlike someone's brother (Mashiba), but Kumi mentions he almost won it (while Ippo apologises for winning.) When Itagaki returns, he mentions he is not in the mood for fun.
Later, while Nanako at Ippo's house waiting for Itagaki, she talks to Kumi on the phone to rub her face in the fact that she and Ippo going out this Saturday. Kumi wonders why she is calling from Ippo's house, and Nanako mentions that is how her and Ippo are, before Ippo takes over the phone to explain things. He tells Kumi that this Saturday he is going to see who Itagaki will face in the Semi-Finals in the Rookie King Tournament, where he promises that he will go out with her next time.
Nanako attends Itagaki vs Imai Kyōsuke match.
Itagaki get sent to Kawai Hospital, where Kumi helps look after him. Kumi tells Itagaki not to use his hand or foot until he is better rested. Itagaki enjoys have Kumi look after him. Imai visits Itagaki, where he gets into an argument with him once Nanako stops by. Kumi returns to yell at Itagaki for not resting, that causes Itagaki and Imai to calm down, which annoys Nanako.
A few days later, Kumi see Itagaki leave the hospital, and she reminds him to rest now that he is released. Ippo picks up Itagaki in a truck, while Imai offers to walk Nanako home, which Kumi comment that Nanako should do it since they would make a good couple. That makes a Nanako a little angry, and tells Imai she though he wasn't suppose to talk to her since he lost the match. Imai walks away determined to beat Itagaki in a rematch. Kumi thinks mean hate to admit they lost, and Nanako mentions that if she has something to lose why wouldn't you try to keep it while walking away. Kumi ponders about her brother that has a match coming up, where boxers never seem to have any time to relax.
with Ippo, Nanako and Itagaki becomes jealous, with the latter thinking Ippo has a cute girlfriend. Nanako disagrees with him since she doesn't think Kumi is his girlfriend.
Nanako attends Itagaki's match before Mashiba Ryō OPBF title match. During the match, Nanako teases Kumi about her "slip" problem.
When she first appeared in the story, she is pretty young, and Ippo comments on her beauty.
A 16 year-old high school student at introduction, Nanako is one of Makunouchi Ippo's biggest fans. Because of this, she views Mashiba Kumi as a rival and competes with her at almost everything. She takes any chance to be around Ippo, and even tried to steal a kiss from him once when he was sleeping after a rough match, but she was interrupted by Kumi. It's shown that she has a perverted side, as when she jumped into pool where Ippo was, she rudely grabbed his penis while stating an innuendo.
Like her older brother Manabu she is very attractive, but she also has the same love for puns as the rest of her family. Imai Kyōsuke is in love with her, but she tends to ignore his feelings as she has no interest in dating her brother's rival.