Isamu Akamatsu (赤松勇, Akamatsu Isamu) is a semi-recurring character in Hajime no Ippo.
Isamu is a close friend with Kizakura Hiroshi and they both joined Kamogawa Boxing Gym after Aoki Masaru's first title match and made him not retire. These three together make the "Aoki Team" with their leader, Aoki. Isamu partakes in boxing training at times and helps Aoki at the Chūka Soba
His surname is Akamatsu. In Japan, surnames are listed before given names.
Isamu and Hiroshi were friends since elementary school and went to a very prestigious private school. Through elementary, middle, and high school, they never lost at competing at grades, letting them get away with anything they want.
Inspired by Aoki's JBC lightweight title match against Katsutaka Imae, Isamu and his friend, Kizakura Hiroshi, encouraged their idol, Aoki to not retire when he was on the brink. Isamu and Hiroshi went with Aoki to the Kamogawa gym to be introduced to the gym members. As Isamu only follow Aoki's orders, he ignored Takamura Mamoru's order of getting him juice until Aoki told him to do it. While Isamu and Hiroshi were sitting around the gym, they were dragged into doing roadwork with Itagaki Manabu and Kimura Tatsuya. As Isamu and Hiroshi were having trouble running, they revealed how hard their past and only like the scent of Aoki because he wins without trying. When Aoki arrived to the group, Isamu and Hiroshi ran to him for comfort.
Isamu went to the Ryōgoku Kokugikan for Takamura's first WBC junior middleweight title defence against Larry Bernard. Isamu, Hiroshi, and Aoki were kicked out by the venue's staff due to them trying to cheer with instrument. In the anime, they did not play instruments, and Isamu and Hiroshi instead expressed how there is a smell of an easy win. After Takamura's win, Isamu ran away with Hiroshi and Aoki due to Aoki being blamed for Takamura getting hit after using the Look Away. Later, since Makunouchi Ippo needed help reviewing his fifth JBC featherweight title defence opponent, Sawamura Ryūhei, Isamu was one of the gym members to be called to Takamura's home to try and help Ippo. The event ended when Takamura got angry due to the large number of people in his room.
When Isamu was walking with Hiroshi, Hiroshi dropped books next to Itagaki containing information about techniques that he and Isamu were gathering, Itagaki grabbed them as he was seeking information about the Dempsey Roll. While nothing was in it of useful information, when Hiroshi held out his hand to grab it from Itagaki, he startled Itagaki which sparked an idea to Itagaki about the Dempsey Roll's methodology and the books were thrown back to them. When Alexander Volg Zangief visited the Kamogawa gym, Isamu and Hiroshi had Volg polish the Statue of Takamura before getting scolded by Itagaki for it.
When the Kamogawa gym members' matches arrived, Isamu and Hiroshi went to the Yokohama Arena. While Kimura was fighting Eleki Battery, the two gave details about Kimura's situation throughout the match. They also brought Tomiko to Aoki's room in the venue to cheer him up. Isamu and Hiroshi wished Aoki good luck, however the two thought that even if he loses, remembering Takamura's bet of giving Aoki Papaya Dachiu's haircut if he loses, it would still be good. When Aoki's match against Papaya began, Isamu watched and cheered for Aoki. During the match, Isamu and Hiroshi could smell that Papaya has the same odour as Aoki. Isamu watched as Aoki's match ended in a draw. When Miyata Ichirō was having his fourth OPBF title defence against Medgoen Dachboy, Isamu and Hiroshi reported to Aoki that Miyata was still fighting in the fifth round. making Aoki leave his room to watch in the audience area.
After Takamura won against WBC middleweight champion David Eagle, Isamu followed everyone as they went to Takamura's house to make sure he went to sleep. Isamu and the others were thrown out as Takamura was unable to sleep with everyone watching.
When Aoki's hairstyle was forcefully cut by Takamura to be like Papaya's, Aoki gained popularity after using the new haircut, which looked like broccoli, to star in a commercial advertising broccoli as "Broccoman." To support Aoki, Isamu and Hiroshi cut their hair just like his and wore the trademark t-shirt. Isamu and Hiroshi arrived to the gym with Aoki to show Takamura how Aoki's Broccoman brand has grown, causing a fight between Aoki and Takamura. to see who is more popular.
As Aoki was angry at Takamura for feeding him the pickled squid that made him sick and was tired of Takamura's actions, he tried to split the gym into two factions, with Takamura being alone and Aoki and the rest of the gym, including Isamu, along with him as Broccoman having the children of Japan on his side. Aoki's side changed from a lot of support to none when Yagi Haruhiko and Shinoda Tomoyuki revealed to everyone about how Broccoman's popularity has severely gone down due to recent reports of Aoki leaving the Kōrakuen Hall while covered in faeces.
Isamu went to the Ryōgoku Kokugikan to accompany Aoki while he waited for his match against Papaya as Kimura fought Eleki and informed Aoki details about Kimura's match. After Kimura's match ended in a draw, Isamu went to the audience area and watched Aoki's match against Papaya and explained to Ippo and Itagaki of Aoki's "operation ineffective action." Isamu watched as Aoki's match ended in a draw.
Isamu and Hiroshi followed Aoki and Kimura as they leave the gym. When Aoki warned Kimura that Itagaki may push him around due to him possibly passing him in the gym's internal ranking, Kimura believed that Isamu and Hiroshi would have his back, however, the duo ignored him.
Being taught boxing by Aoki, Isamu and Hiroshi began hitting the sandbags, with Isamu using the Flicker Jab, leaving the gym members in shock. Upon Aoki's order Isamu and Hiroshi introduced themselves to Ippo, Kimura, and Itagaki as Team Aoki. The duo ignored Itagaki's attempt of trying to teach them a One-Two and Ippo's encouragement to become a pro boxer. Isamu ran to Aoki as Aoki explained how Isamu and Hiroshi don't want to become pro boxers, just wanting to hit the sandbag for fun. When Kurita Baron arrived to the gym, Baron's attitude made Isamu and Hiroshi run out of the gym in fear.
As Aoki's Chūka Soba has been getting busier and advertised on TV, he hired Isamu and Hiroshi of Team Aoki to work there and had to close early due to the demand. After closing, Kimura and Itagaki entered and Isamu and Hiroshi were tasked to make ramen for them and Aoki. When the three boxers were discussing Isamu and Hiroshi's report chart about their boxing skills, Isamu and Hiroshi advised the three to step back when they look at Aoki's chart due to his ratings are so big that they surpass the paper's border. Isamu and Hiroshi went to the Yokohama Arena and watched Aoki and Kimura's matches against Ponsa Kureck and Sim Rex respectively, which ended in Aoki and Kimura's loss. Afterwards, Itagaki had the two watch over Aoki and Kimura to take them to the doctor if anything happens while they watched Miyata's match against Randy Boy Junior and Takamura's match against Ronald Duck, which both matches ended in Miyata and Takamura's victory.
When Takamura ate at the Chūka Soba and talked to Aoki, Isamu and Hiroshi were in the back cooking.
After Ippo defeated Kojima Hisato in his eighth JBC featherweight title defence match, Kojima received an autograph from Aoki. THe autograph was then thrown in the trash and was found by Isamu and Hiroshi. The two urgently reported to Aoki, prompting the three to go find Kojima.
When Aoki and Kimura's comeback match since their loss in the Class A Tournament arrived, Isamu went to the Kōrakuen Hall. Isamu watched Kimura end his match in an eight round draw and Aoki win his match by knockout in the eighth round.
At the Chūka Soba while Aoki, Kimura, and Itagaki were talking about Miyata's eighth OPBF featherweight title defence match, Isamu was in the back cooking. Later after Ippo was in shock for hitting Taihei, Umezawa walked him to the Chūka Soba, where Isamu was seen in the back cooking.
Isamu is seen wearing a red and purple striped long sleeve shirt and long black pants.