He is a former JBC junior featherweight champion before relinquishing his title to move up in the featherweights in order to fight Makunouchi Ippo for his JBC title. He retired due to preferring to continue his dream as a doctor instead of a boxer in the professional ring.
Before Sanada was born, he had his path set by his father to become a doctor. Despite not disliking medicine, Sanada came across the Kinoshita gym in an ad and decided to go there to relieve some stress by hitting the sandbag. Six months later, he attempted sparring and got beaten in his first sparring match. After further studying the human body, he returned and successfully defeated his opponents in the professional ring using his knowledge of medicine. After becoming the JBC junior featherweight champion, he went up a class in order to face a man stronger than him as a way of challenging himself.
After the JBC junior featherweight title match between Hayami Ryūichi and Kobashi Kenta, Sanada introduced himself to a nervous Makunouchi Ippo and Mashiba Kumi. however, when they were about to shake hands, they were stopped by Sanada's trainer, Hama Dankichi, due to his beliefs that enemies have no business shaking hands. Later, during a training session, Sanada downed his sparring partner after penetrating his guard with his Tsubame Gaeshi, which Sanada predicted to be able to break Ippo's Peek-a-Boo Style.
While at the Imperial College of Medicine, Sanada was approached by reporter Īmura Mari, who he told that he would not talk about his new technique as instructed by Dankichi. Mari instead interviewed Sanada about why he started boxing despite having a medical career path set for him. After he told her the reason, he revealed that he moved up a weight class to challenge himself by fighting Ippo.
Sanada participated in a public sparring match against a junior lightweight boxer ranked third in the JBC three weeks before the title match in order to demonstrate his skills. When the match began, Sanada displayed the Hien and used his ability to analyse how damaged his opponent was and whether he could continue or not, dodging all his punches. Between a round, Sanada was calmly taking his pulse in order to enter the next round at full speed. Sanada continued to beat his opponent, throwing an uppercut to show his Tsubame Gaeshi to the reporters, however, his opponent fell at the first uppercut, ending the spar.
A few weeks later, while playing video games with his coach's daughter; Kinoshita Tsugumi, Sanada began to reflect on how he he could not cure the worries of the patient's families, and needs to become stronger. He remembered how despite being the champion, he had never been tested and believed that Ippo is the right person to finally prove how strong he is. At the weigh in, Sanada expressed how he wished Ippo would act more prideful about the belt that went from Date Eiji to Sendō Takeshi before getting to him. Walking away from the Kōrakuen Hall after shaking hands with Ippo, Dankichi mentioned to Sanada that his words served to put more pressure on the champion despite Sanada not wanting it to as he wants Ippo to be at his best, otherwise he would not be able to know how strong he really is.
On the day of the match, Sanada entered the ring, and, when Ippo arrived as well, the match began. As soon as the gong rang, Sanada hit Ippo with a right straight that caused him to panic. Sanada took advantage of the situation and attacked Ippo, forcing him onto the ropes and, with his palpation ability he attacked him for five seconds until Ippo recovered from Sanada's right. Ippo attempted to get into his rhythm and went towards Sanada, however Sanada hit him and proceeded to use his Hien to change his jab into a hook. Sanada continued to use his Hien to keep Ippo at bay until the round ended.
The second round began with Sanada being approached by Ippo, who dashed immediately from the opposite corner. When Ippo began his Dempsey Roll motion, Sanada pushed his body on Ippo's chest, stopping the motion. With distance between them, Sanada stopped Ippo from attempting another Dempsey Roll by using his Hien, following up with more punches with his Hien, not wanting Ippo to use the powerful technique. Sanada continued hitting Ippo's Peek-a-Boo Style guard at the ropes until he decided to break it by launching an uppercut that got blocked and then immdiately a second uppercut, using the Tsubame Gaeshi. The second uppercut of the Tsubame Gaeshi slipped through Ippo's guard and hits him, sending his head flying upward. Sanada then became surprised when Ippo recovered and attacked him, sending Sanada back. After Sanada got attacked with multiple punches at the ropes, the two switched positions when Sanada landed a hit. Sanada then used his Tsubame Gaeshi on Ippo's stiff guard, with the second hit hitting Ippo through the guard, making him go down to his knees. After Ippo got up, the second round ends before either could land another hit.
When the third round began, not wanting to let Ippo recover, Sanada rushed towards him and used the Hien. Sanada then used his Tsubame Gaeshi, with the first uppercut hitting Ippo's guard, however the second uppercut could not hit Ippo's face, as Sanada's second uppercut was blocked by the Cross-Arm Block. Sanada countered the block by using hooks as Ippo drew closer. Sanada was then hit by a body blow, causing Sanada to have to commence an in-fight with Ippo due to the blow effecting his legs. Sanada lost the in-fight battle after going down due to several hooks. While downed, Sanada checked the damage on his body and estimated when parts of his body would recover. After the check-up, Sanada got up and clinched when Ippo got close, not wanting to fight close ranged as his eyes had not fully recovered. When the clinch broke, Sanada's hits to Ippo's head shook his superior canal in his inner ear, making the champion lose his balance. When Ippo's balance came back, Sanada threw punches with his Hien, however, since they were weaker, Ippo managed to get close. The round then immediately ended.
In the fourth round, as instructed by Dankichi, Sanada got into an in-fighter's range and got close to Ippo while blocking and dodging punches, delivering body blows at vital points, making Ippo's face blue due to cyanosis. As Ippo began to lose balance from the body blows, Sanada used his Tsubame Gaeshi, but Ippo blocked the second uppercut by putting one of his hands between the attack and his jaw, still causing damage. As Samada continued his attack, he noticed Ippo was at his limit and throws a right, making Ippo start to fall. Ippo barely managed to stop his fall by hanging onto the ropes. When Sanada noticed Ippo's light returning to his eyes and Ippo released a punch that missed, the fourth round ends.
To Sanada's shock, Ippo dashed towards him as the fifth round began and Sanada was relentlessly attacked. Sanada then noticed that Ippo was beginning to use the Dempsey Roll, stopping the motion by pushing his body on Ippo's chest. Sanada was then hit by a liver blow due to Ippo anticipating Sanada's action. As Sanada began to fall, he was hit by a Gazelle Punch. Continuing his knockout pattern he used against Sendō, Ippo used his Dempsey Roll on Sanada until Ippo ran out of energy. Ippo attempted to hit Sanada, who withstood all of Ippo's punches, however, Ippo's right barely grazed Sanada's cheek. Believing that he was now the winner, Sanada launched a finishing right. However, he fell down from the momentum and missed the champion, causing a down. The referee then signalled the end to the match, with Sanada losing the match.
In his waiting room, Sanada satisfied after lasting through the Dempsey Roll, decided to retire and focus on his medical career, thanking Dankichi for his help. Mari urgently informed Sanada that Ippo went to sleep and started snoring. Seeing this as a dangerous symptom, Sanada went to Ippo's room and checked on him. As he checked the pulse, he noticed something that made him react in a way that made everyone worry, but Sanada claimed Ippo was simply asleep due to fatigue but would be fine. When asked why he reacted that way, he answered that despite being unconscious, Ippo held on to the belt so strongly, that no one would be able to take it away from him.
When Ippo was looking for help on learning about the detached retina disorder due to suspicions of Takamura Mamoru having it, Sanada was approached by him at his college. Sanada praised Ippo's strength, as he has gotten stronger since the time the two fought, and noted how Ippo has never received a down sine their match as well. The fact that Ippo doesn't fall frightens him, however, due to the damage to his body can accumulate, slowly destroying his body without realising it. Sanada worryingly asked Ippo if he was experiencing symptoms of accumulative damage, which he replied that he doesn't, much to Sanada's relief. Sanada learned that the need for his advice was for someone else and for his eye.
Sanada began to explain retinal detachment, which, when the retina detaches, water gets in the wound until the retina is completely separated from the eye. He explained that the possibility of their vision being affected is high, but how much depends on the location of the opening, where the top opening would be faster and have more symptoms, and the lower would be slower with less symptoms. With Ippo now knowing how dangerous retinal detachment was, Sanada stressed that he must not allow an athlete to fight with the condition, as it can lead to blindness, and if left untreated, the cells around the gash will die and the eye would decay, making the person have to get a fake glass eye. Sanada revealed how retinal detachment is curable, with the sooner the condition is healed, the boxer can return with limitation. Sanada demanded for Ippo to take full responsibility for the boxer to take surgery, since if the boxer he cares about went into the ring with the condition, he could lose his life. Sanada hoped that Ippo was wrong about his suspicions about Takamura, who Sanada knew was the one he was talking about due to the way Ippo was trying to prevent making a big deal before his world title match. Sanada left, promising to keep their conversation a secret.
When Sanada learned that his former kōhai, Karasawa Takuzō is going to challenge Ippo for his JBC featherweight belt, he visited the Kinoshita gym in concern. He warned Karasawa that Ippo is strong and is not the same as when Karasawa saw Sanada fight him before. However, Karasawa noted that he is not the same as before either, and wanted to spar with Sanada to show him his Dempsey Roll countermeasure, but Sanada did not want to since he is not as strong as when he was a boxer. Karasawa revealed how his odds leave him at a 30% chance of winning, but saw that it is still worth taking the title match, which Sanada agreed. When Karasawa asked Sanada about Ippo's punches, Sanada described how they are not normal, a comment that did not faze Karasawa from wanting to fight Ippo. Sanada left the gym, impressed by Karasawa's confidence, but despite believing that Ippo will win by knockout, he is still excited as Ippo may still lose due to the pressure of being expected to win easily.
Later, Sanada observed Karasawa's training, where Kinoshita steps on his torso to build up endurance against the Dempsey Roll, seeing that Karasawa knows what he is doing against the technique. Sanada commented to the gym members how bad Ippo's body blows are, believing that Karasawa's training method won't be enough against the Dempsey Roll. After Karasawa took a break, Sanada warned Karasawa that Ippo will try to stop his movements with body blows. As Karasawa replied that he would build a body that can take any number of body blows, Sanada wondered what would happen if Karasawa was able to stop Ippo, something that many have failed to do. When Karasawa's weigh-in with Ippo arrived, Sanada went to the Kōrakuen Hall, where he meets Ippo. After the weigh-in, Sanada informed Karasawa how Ippo's back seems to have grown a size larger and that he is in perfect shape physically. Karasawa was glad that Ippo is at his best, however, Sanada wondered if Ippo is at his best, since his expression is the same as before Sanada fought him, unable to hide his anxiety of his first title defence. Sanada assumed that Ippo is out of his game, advising Karasawa to take advantage of the fact. Sanada mentioned how Tsugumi told him that Karasawa was worried about the gym and his coach, which is why he is helping, but Sanada warned Karasawa that even a distracted Ippo is very strong.
The next day, Sanada arrived to the Kōrakuen Hall for Karasawa's JBC featherweight title match against Ippo to be one of Karasawa's seconds. When Sanada arrived to the ring with Karasawa, Karasawa asked if Ippo looked complete, which Sanada confirmed that he is perfect. Sanada advised Karasawa to not take the opening hit and to dodge Ippo's punches for the first round in order to remember his range and rhythm. After the first round, Sanada noticed how frightening a boxer Ippo has become after observing how Karasawa's mouthpiece is bloody despite Ippo not landing any clean hits as they were blocked and Karasawa's condition is poor despite being good at the start of the round. Sanada told Karasawa to continue the hit-and-run tactic for the second round. During the second round, Sanada realised that Ippo is not going to use his Dempsey Roll that Karasawa expected, yelling out to him to get out of the corner as Karasawa was trying to find a chance to counter the Dempsey Roll when he uses it. When Karasawa was falling from Ippo's final attack, Sanada was about to throw in the towel before being stopped by Kinoshita. After Karasawa lost by knockout in the second round, Sanada went with Karasawa to his venue's room. Karasawa regretted not being able to draw out Ippo's full power as Ippo sealed the Dempsey Roll, however, Sanada disagreed, knowing that Ippo doesn't hold back and that he in fact faced the true form of Ippo, making him having fought the most dangerous part of Ippo. Sanada became intrigued to see Ippo's infinite potential and his Dempsey Roll once the seal is released.
Sanada went to the ōrakuen Hall to watch Karasawa's match in the Class A Tournament against Itagaki Manabu. Before the match began, he met Ippo, telling him how he saw his match against Wally, and tried to get information about Itagaki's condition from him. After Saeki Takuma approached the two, Sanada, Saeki, and Ippo sat at the audience area with each other as Karasawa and Itagaki's match was about to begin. As Karasawa and Itagaki were making their entrance, Sanada told Ippo and Saeki the information he learned about Itagaki from watching tapes with Karasawa, and that while Itagaki is faster than Karasawa, Karasawa once mentioned to him that it felt like Itagaki was slower. During the first round, Saeki wondered why Karasawa was able to hit Itagaki when he went for a counter since Karasawa should be slower even when he shifted up a gear when Itagaki did the same. Sanada explained that Karasawa shifted down a gear to change the timing of his punches, making it difficult for Itagaki to time his counters. As Ippo was about to leave to tell Itagaki's corner about the information, Sanada guilt Ippo into not doing so. Sanada watched as Karasawa lost by knockout in the second round. Sanada believed that Karasawa made the right decisions in the match, however, he ran out of strength as Itagaki was simply stronger. As Saeki left, he claimed that he was glad that Itagaki's right did not hit Karasawa, which led Ippo to think that he was worried about Karasawa, however Sanada knew that he meant that he was worried that Itagaki's hurt right fist would have broken if it landed, as Saeki wanted to face Itagaki in his best condition. Sanada was interested to see who is the fastest in Japan between Itagaki and Saeki. Sanada went off to Karasawa's dressing room to console him.
|16||LOSS||13-2-1||1994-04-07||Makunouchi Ippo||Tokyo, Japan||5(10), 2:33||TKO||"FIRST STEP"|
JBC Featherweight Title Match
|15||WIN||13-1-1||1994-03||Unknown||Tokyo, Japan||7(10)||KO||JBC Junior Featherweight 5th Title Defence Match|
Relinquished belt and moved to featherweight
|14||WIN||12-1-1||199X||Unknown||Tokyo, Japan||?(10)||N/A||JBC Junior Featherweight 4th Title Defence Match|
|13||WIN||11-1-1||199X||Unknown||Tokyo, Japan||?(10)||N/A||JBC Junior Featherweight 3rd Title Defence Match|
|12||WIN||10-1-1||199X||Unknown||Tokyo, Japan||?(10)||N/A||JBC Junior Featherweight 2nd Title Defence Match|
|11||WIN||9-1-1||199X||Unknown||Tokyo, Japan||?(10)||N/A||JBC Junior Featherweight 1st Title Defence Match|
|10||WIN||8-1-1||199X||Unknown||Tokyo, Japan||?(10)||N/A||JBC Junior Featherweight Title Match|
|Preceded by||Title||Succeeded by|
|Unknown||JBC Junior Featherweight Champion||Kobashi Kenta|
Sanada has short dark brown hair with bangs going over his forehead. Unless in the ring, he wears black eyeglasses over his black coloured eyes. He also has long eyebrows, and a somewhat large nose.
When Sanada first meets Ippo, he wears a white shirt under a dark coloured opened coat, along with black pants and a scarf around his neck. During a sparring session to test his Tsubame Gaeshi and after his match with Ippo, Sanada wears a black shirt. When Sanada did his ring entrances, he wore a robe. When he was in the ring, Sanada wore blue boxing trunks with a yellow vertical stripe at the sides. While at the Imperial College of Medicine, Sanada wears a white business shirt with a blue tie under a white lab coat.
Sanada is known to be confident in himself. He is a very kind man, even to his opponents, as well as incredibly smart. Sanada is eager to challenge himself, moving up a weight class to fight Ippo just for a challenge and wanting to fight him at his best. Sanada admired the JBC featherweight belt even when he was a junior featherweight, admiring the former JBC featherweight champions Date Eiji and Sendō Takeshi, not liking it when Ippo seemed to show little pride of his own belt. He seemed to act strange when Iimura Mari was talking, most likely not wanting to discuss his past.
Being a former Japanese champion, Sanada was a highly skilled boxer. His fighting style focuses on skill and strategy rather than overwhelming strength or speed. Sanada's boxing involves his knowledge of the human body to drive in major attacks at pinpoint precision to stop and breakdown his opponent from the inside rather than attacks to the body that do major external damage. His techniques allow him to drive in major attacks with even the slightest opening in an opponent guard. His understanding of anatomy also allows him to target the 4 vital organs of the body, which would lead to cyanosis.
Sanada himself has no outstanding weaknesses. He lost to Ippo because he was too focused on his strategy of lowering Ippo's stamina. This might be more of a fault of Hama Dankichi than Sanada, since it was Dankichi who instructed Sanada to focus on that strategy. Considering his intelligence, it is possible Sanada would have developed Sawamura Ryūhei's strategy had he focused on countering the Dempsey Roll instead.
Main Article: Sanada Kazuki/Gallery
- Sanada was modelled after the boxer,Salvador Sánchez. Before being killed in a traffic accident, he wanted to become a doctor.
- The video game system Sanada was playing on with Kinoshita's daughter bears a striking resemblance to the original Xbox, though the controller is a cross between the Xbox's and PlayStation's. The two game cases sitting next to the console read "Megamix 200X" and "Buyo". The fighting game they were playing feature two male characters with similar appearances to that of characters from the Seint Saiya anime.
- Chapter 291, page 14, Sanada took down the first ranker.
- Chapter 290, pages 17-18, Sanada titled as a former junior featherweight boxer.
- Chapter 293