The Proof of Power Arc, is the nineteenth story arc in the series and the fifth in the New Challenger Saga.
Ippo Makunouchi's second JBC featherweight title defence is against Hammer Nao, otherwise known as Naomichi Yamada, a previous kōhai of Ippo who once joined the Kamogawa Boxing Gym before having to move from Tokyo. Manabu Itagaki also joins the gym, who looks up to Ippo as a senpai, similar to how Yamada did in the past.
Summary[]
New and Old Kōhai[]

Itagaki arrives at the Kamogawa Boxing Gym.
Ippo discusses when he recently received a baton pass from the retired Date at the hospital with Takamura, Aoki, and Kimura. They then discuss Ippo's second JBC featherweight title defence, with the opponent ranked 7th and having a ring name called "Hammer Nao" from the Hachinohe Boxing Club who they assume is foreign. Later, as Ippo does mitt-training with Kamogawa, someone enters the gym. The person tells Aoki and Kimura he is a new student, making the two mad when he claims to not know their names. Yagi then arrives at the gym and introduces the person as Manabu Itagaki, who placed second in the intern-high national. Itagaki mentions the reason for joining the gym is because he respects a member of the gym. Takamura assumes it is him, but it is in fact Ippo, who he views as a senpai. Kimura decides to show Itagaki the pain of being a professional by doing a roadwork session.

Kamogawa gym members discuss Ippo's title defence against Hammer Nao.
Itagaki falls slightly behind Ippo in the roadwork session, while beating Aoki and Kimura. Remembering Naomichi Yamada, Kimura believes that Ippo's boxing brings others to him, possibly already taking Date's place. Takamura disagrees, claiming Ippo has a weakness, lacking stability making him unable to tap into his full power at times due to being mentally weak. Takamura adds that one has to defeat anyone who appears in the ring and if one can not fight like a demon, they will not live up to the title of being a leader. When they return to the gym, Kamogawa has Yagi show Ippo and the others tapes of Hammer Nao's matches. While everyone is watching the tapes, Yagi notes Hammer Nao's hook to the body being his speciality and how he went from junior welterweight to featherweight to fight Ippo. Ippo then recognises that Hammer Nao is his former kōhai, Yamada Naomichi, whose appearance has changed due to him shaving his head and eyebrows, looking more intimidating. Takamura, Aoki and Kimura are in disbelief while Itagaki predicts the match will be easy for Ippo. After Ippo leaves the room with the tapes, Itagaki questions why Ippo looked tense over an easy opponent. Takamura and Kimura knows it will be difficult for Ippo to fight Yamada, while Aoki is not so happy about being the semifinal for two of his kōhai.
That night, Ippo watches the tapes in his room. He was thrilled that Yamada looked strong and used courageous tactics, however, Ippo questions if he can hit his first kōhai, and why Yamada chose to challenge him. At the Hachinohe Boxing Club, the Hachinohe coach asks Yamada why his opponent has to be Ippo when he believes Yamada is a wonderful fighter, remembering his previous boxer, Jason Ozuma losing to him when he had potential. Yamada answers that he knows Ippo's strength and that knowing who he is fighting makes it easier to defeat him. While the Hachinohe coach questions if Yamada can hit the boxer that brought him into boxing, Yamada tells him that he can and that he will beat him. Later, the poster for the title match is placed on the Kamogawa gym. Itagaki notices that Yamada is not imaged on the poster, which Yagi mentions that Yamada is a name near worthless for him to be shown on the poster. Ippo is unable to hit Kamogawa's mitts in full force due to seeing Yamada's face on them, causing Kamogawa to quit the session. Mari enters the gym and reveals that Yamada went from Aomori to Tokyo and, when she interviewed him, he told her that he would not be holding back.

Mari talking to Ippo about Yamada.
Aoki and Kimura goes to the Nerima Boxing Club where Yamada is training and witnesses Yamada sparring where Yamada defeats three sparring partners with a body blow that causes them to throw up. Yamada then goes outside where he meets Aoki and Kimura which he assumes they were gathering information. Aoki and Kimura attempts to have a lighthearted conversation with their former kōhai, however, Yamada only provokes them with taunts and requests for them to inform Ippo that he will be seriously coming for his belt. Elsewhere, Ippo and Mari discuss the information Mari gathered about Yamada. Mari tells Ippo that Yamada is an underdog, a boxer going into the ring knowing they will never win. Mari came to that conclusion by looking at his record of eight matches. She explains that Yamada went to other gyms as an unknown boxer looking to fight their best boxer and winning while getting brutally beaten in order to go through the fastest path to the title in order to fight a dream match that is a calibre of a world title match: fighting Ippo. Ippo becomes saddened after hearing that, however, he realises that he has been chosen as Yamada's goal, deciding to answer Yamada with his fists. While training, Kamogawa informs Ippo that the fight will be a close ranged one and they both know that the Dempsey Roll can not be used due to the distance being too close to use it.
PROOF OF POWER - JBC Featherweight Title Match - Makunouchi Ippo VS. Hammer Nao/Aoki Masaru VS. Paddy Magramo[]

Ippo and Yamada at the weigh-in.
During the weigh-in at the Kōrakuen Hall a day before the match, Ippo meets Yamada. After the weight check, Yamada does not accept Ippo's handshake, but thanks him for teaching him about boxing and that he is giving him the belt. Ippo responds by claiming that while they practised together, he never taught him how to take the belt. The next day at the Kōrakuen Hall, the semifinals begin with the 5th ranked in the JBC Aoki, who boasts how he is an underdog hunter, having to fight against the Philippines 10th ranker Paddy Magramo. Aoki and Paddy both scored downs and the match ended in a decision win for Aoki. In the waiting room, Yamada expresses how he is scared of Ippo's punches, but he is happy that Ippo is serious about the match, wanting to tell Ippo in the ring that he has tried his best in the two years of boxing and has gotten strong. He then reveals that he will retire as he will be happy regardless of the result, having no intention of going to the world stage. The Hachinohe coach supports his decision, urging him to tell Ippo what he has done for the past two years. As the match is about to begin, Ippo heads to the ring and plans to go at full power. While walking to the ring, Yamada notices the wall that Ippo previously showed him that had marks on it, hitting the wall until he gets stopped by his coach to prevent injuries to his fists while wishing for Yamada to take the title for him.

Ippo and Yamada fighting.
With both in the ring, the match begins. As the gong sounds, Ippo immediately gets close to Yamada and delivers powerful combinations that sends Yamada down when Yamada tries to side-step away. Right as Yamada gets up, Ippo rushes again at Yamada, this time Yamada clinches Ippo, however, Ippo quickly pushes Yamada back and breaks the grab. Yamada attempts to hit Ippo many times without success until Ippo lands a hit and begins a combination of punches again. Takamura notices that Ippo is rushing the match in an act of desperation. After getting hit, Ippo downs Yamada again after a combination of punches. To Ippo's dismay, Yamada stands back up. Yamada enters the Peek-a-Boo Style and waits for an opportunity to strike as Ippo punches his guard at the rope. Yamada retalites and throws a body blow that hits Ippo's block, which the blocked punch causes Ippo's feet to lift off the ground. Yamada and Ippo then get into an exchange of punches where Yamada aims for Ippo's body as Ippo lands hits on Yamada's face until the first round ends. Yamada, irritated as their fight was just beginning, hits the ring's ropes in disappointment. In the corner, Yamada is instructed to use the body blow that will affect Ippo: the solar plexus blow. Ippo is told the three meanings to be a pro: to do any job with ease, to answer the customers demands, and to devote one's self to the fight.

Yamada hitting Ippo with the solar plexus blow.
When round two begins, Ippo predicted Yamada's body blow strategy and blocks his body blows. Yamada counters the guard by missing a hook and returning his opened hand onto Ippo's elbow, prying his guard open. With his guard open, Yamada lands the solar plexus blow, stunning Ippo, who can not breathe and lands a clean one-two. Yamada continues landing punches on Ippo and, when Ippo attempts to guard again, Yamada uses the previous tactic to open Ippo's guard to continue his attack after another solar plexus blow. While Yagi claims that it is against the rules as Yamada's using his opened hand to open the guard, Kamogawa praises Yamada for it as a foul has not been called, believing that avoiding being called on his fouls is an art form. As Yamada gets Ippo to the ropes and lands the third solar plexus blow, Aoki realises that Yamada never used the solar plexus blow in his matches before, leading Takamura to note that Yamada had trained his legs to do anything he is told during a match. While blocking Yamada's punches, Ippo acknowledges that Yamada is strong, but believes there is one thing he does not know. Ippo opens and lowers his stance, inviting him to attack.

Ippo trying to catch Yamada as he falls.
Yamada responds by dashing in and hitting him multiple times. After receiving a solar plexus blow, Ippo lands a liver blow, knocking Yamada immediately down. Ippo wishes to teach Yamada the one thing he does know: what losing is like. Yamada gets up, wanting to continue his personal world title match as long as he is conscious. After blocking a one-two a liver blow, Ippo successfully delivers a one-two and liver blow of his own, along with a combination of attacks that sends Yamada falling. Ippo attempts to catch Yamada's fall, however, the referee steps in and signals an end to the match, resulting in Ippo's second JBC title defence win. Ippo is interviewed, and he comments that he did not want the match to last long and that when it was painful during his first lost against Date, but it taught him a lot about boxing. He ends the interview claiming that he believes that Yamada will be stronger when he returns to the ring.

Yamada thanking Ippo.
At the changing room, Kamogawa advises for Ippo to not see Yamada, as Ippo's comments may make Yamada hold a grudge, believing that the winner has nothing to say towards the loser. Yamada tells his coach that he is satisfied about the outcome of the match. He then claims the need to apologise to his mother, as when Ippo said he would be stronger, he felt his words would be gone to waste if he retired, deciding against his earlier decision to retire and decides to continue boxing. Yamada and his coach then sees Ippo from a distance. The coach insists for Yamada to properly greet him, however, Yamada believes he already had their conversation in the ring. Yamada then vows to himself to chase the vision of Ippo's back for eternity, thanking him. As Ippo showered, he realises that Yamada was strong, still feeling the pain of his punches.
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Proof of Power Arc | |||||||||||||||||||
Manga Volumes | |||||||||||||||||||
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38 | 39 | 40 | |||||||||||||||||
Manga Rounds | |||||||||||||||||||
341 | 342 | 343 | 344 | 345 | 346 | 347 | 348 | 349 | 350 | ||||||||||
351 | 352 | 353 | 354 | ||||||||||||||||
Anime Rounds | |||||||||||||||||||
9 | 10 | 11 | 12 |