Tomoko Yamaguchi (山口 智子, Yamaguchi Tomoko), often referred to as Dr. Yamaguchi, is a semi-recurring character in Hajime no Ippo.
After being recommended by to see Yamaguchi, Makunouchi Ippo went to see her. Yamaguchi told him that she heard his situation and began to give him a checkup. She informed him that the reason for his injuries is the fact that the muscles of his arms can not withstand the punching power he has. She then told him that he will be able to fight in the next match but also warned him about the dangers of it. In order to able to punch full power without getting injured, she revealed that Ippo must develop his shoulder muscles.
Later on, Yamaguchi visited Ippo while he was training with Kamogawa Genji and Takamura Mamoru. As they trained, she noted that the training also improved back and shoulder muscles, which was the best thing for Ippo. Both the doctor and Kamogawa agreed that unless Ippo was one hundred percent, he would not be able to fight. Yamaguchi mentioned that she can give Ippo a pain killer to help kill the pain in his fist for his match.
In Osaka, Yamaguchi met Ippo prior to his weigh-in. After greeting Yamaguchi, Ippo went to the weigh-in as the finals for the All Japan Rookie King Tournament began. In the locker room, Yamaguchi examined Ippo's fist and determined that due to his pain, the only solution is to give him a shot. She also warned him that by feeling no pain, he would not be able to know if he gets a worse injury. After taking the pain killers, Ippo could now punch, even though he did not feel anything. Yamaguchi watched Ippo fight and defeat Sendō Takeshi in the match. After the match, Yamaguchi went out celebrating with them to celebrate Ippo's win. Takamura and Kamogawa ended up getting into a fight over her.
After a month had passed, Ippo got his right fist checked by Yamaguchi, who informed him that it was completely healed.
In order to defeat Alexander Volg Zangief, Kamogawa had Ippo go through a harsh training menu that was taking its toll on him. Yamaguchi visited Ippo's home to give him a massage as requested by Kamogawa. When She heard about Ippo's training menu on top of his normal practice, she realised that his stamina could last for eight rounds. By feeling his muscles, she learned that he built up muscles that could store more oxygen than before. She also noted Ippo's defensive power went up, as the springs in his legs have the ability to force things up but also absorb damage. She was impressed with Kamogawa's menu since every exercise that he had Ippo doing was for a specific result.
When Ippo visited Yamaguchi for a check up before his title match against Sendō, She warned Ippo that while there was nothing wrong with his fists, Ippo is more prone to hurt them again. As she was about to give Ippo a massage, she noticed Ippo's back muscles are bigger. Yamaguchi noted that while chopping wood would increase power, the greater the power, the more prone he is to injure his fists. To prevent this, Yamaguchi gave Ippo a shock absorption rubber to put it under his bandages.
While Ippo was training for his match against Sawamura Ryūhei, Yamaguchi received a call from Kamogawa to go to the gym. When she got there she was asked to perform an emergency checkup on Ippo by Kamogawa. After being surprised about Ippo's increased muscles, she noted that there were too much strain put on his waist and knees, noticing an accumulation of inflammation due to a heavy amount of stop and go motion as well as an odd twisting motion. She warned that putting more stress there is dangerous since injuring one's waist and knee muscles can end an athlete's career. She advised him if he wanted to use the Dempsey Roll, to use it only two times, otherwise his life as an athlete is over.
When Ippo's match against Sawamura arrived, Yamaguchi watched as Ippo wins the match. After the match, Takamura carried Ippo to the waiting room after he collapsed in the ring, where she was waiting. As she checked Ippo's conditions, she mentioned that the New Dempsey Roll should have hurt him, and if there is any serious damage it will effect his career. After the checkup, she revealed that there are tearing of the muscles fibres, some blood vessels burst, and his ligaments were slightly hyper extended, believing that his tough muscles saved him. She assured that there were no career ending injuries, relieving everyone in the room. After Ippo went home with Mashiba Kumi, Kamogawa asked her what she thought about Ippo's condition. She answered that his body is hurt quite a bit, and If Ippo used the new Dempsey Roll anymore in the match, he might have gained permanent damage. She added that Ippo must rest, but after recovery, Ippo would throw that punch again, which will continue to hurt his body. However, Yamaguchi believed if Ippo strengthened and reinforced his middle or lower body, he may be able to use it without any pain.
Yamaguchi was visited by Ippo after his match with Sawamura. Yamaguchi, worried about Ippo's left knee, gave Ippo a crutch and advised him to not do any practise or exercise. Yamaguchi ordered him to not rely on the Dempsey Roll as it causes great stress on his body and will shorten his life as an athlete and cause him an early retirement upon continued use. She suggested to limit the use of the Dempsey Roll if Ippo has things he wants to still accomplish, adding that he should have the power to win even without the Dempsey Roll.
After becoming the World Champion of WBA and WBC Middleweight Class, Takamura mentions that they want him to accept the People's Honor Award. Takamura heads to Yamaguchi's to get his leg worked on after he injured his foot in his fight. Yamaguchi tells him that his heel bone doesn't look good, and back of his calf is in pretty bad shape. She continues to check him out, while her breast is touching his foot, which ends up exciting Takamura.
She asks Takamura to turn over, and he comments that she might have been poked by something hard, and not to worry since it happens all the time. She doesn't respond, and Takamura continues to brag until Yamaguchi mentions that Ippo comes there all the time. Takamura is shocked, and charges at Yamaguchi for being compared to Ippo, but he ends up getting throw out of a window in his underwear instead and causing an incident later. His Award ends up getting cancelled.
Takamura keep going to Yamaguchi Clinic in order to get treated. After Takamura's victory parade, he visits Yamaguchi against for another massage. Takamura was bragging on how big his parade was (even though no on shown up.) Takamura continues to brag about his fame, and Yamaguchi mentions that she can help celebrate next time. During the massage, Takamura's foot brushes Yamaguchi's breast again.
She mentions that she did Judo, where she knows how nice it is someone flying, but she never hit anyone before. As she is throwing punches in the air, her chest continues to rub against Takamura's foot, while mentions that she wonders how it feels to punch someone. She tells Takamura his exam is done, while Takamura mentions that he wants to show how good it is to let someone have it. He proceeds to jump attack her again and she kick throws him out the window again. Takamura's underwear fall of him in the process and proceeds to run away naked.
Ippo visits Yamaguchi to get her opinion on hand and ankle weights, and how to use them. She first advise Ippo against using them to strengthen the new Dempsey Roll, but tells him to take things slowly in order to prevent any potential strain on his body.
Later, she goes to Funa Bowl to check up on Ippo for Kamogawa Genji. She notices that it looks like Ippo is taking part in a Bowling tournament with Aoki Masaru, Kimura Tatsuya, Takamura Mamoru, and Itagaki Nanako. Takamura thinks she is there to see him, since he has been visiting her in the past in order to try to sleep with her. She mentions that she will only sleep with Takamura if he begs for it. However, Takamura's pride doesn't allow him to beg for it, even thought Kimura and Itagaki tells him they would.
Nanako disappointed that Yamaguchi shown up. Yamaguchi is surprised to see Ippo is betting with them while wearing weights on his wrists and ankles. Nanako mentions it is for drinks, but he can't beat Aoki but the other three. Ippo is able to get a strike again. Yamaguchi notices it takes a lot of strength and rock solid stability to do that with one leg in the air. She thinks Ippo's leveled up his natural born strength, and balancing from working on the fishing boat, where it is a fusion of power and flexibility. She tells Ippo that Kamogawa Genji asked to check up on him, and that he is waiting for his return at the end of summer.
Later on, Kamagawa visits Yamaguchi in order to give his thanks to her for help with Ippo. When he arrives outside her clinic, he finds Takamura getting thrown out a window naked by her. She calls the cops on Takamura, and they end up running away together.
Yamaguchi is known by most of the characters to be extremely physically attractive. She has a voluptuous figure and large breasts. Takamura usually tries to sneak peeks at her body. This happened once at Ippo's celebration dinner for his winning the All Rookie Tournament, where Takamura tried to look at Yamaguchi's thong through her panty line when she was drunk and bending over.
- Yamaguchi's nickname, Onna Sanshirō (女 三四郎), means Sanshirō Woman/Female, where it gets it named from Sanshiro Sugata, since the character Sanshiro was regarded as a master of judo.