Incoming 40th Inter High Events
Koga is trying to fix Kinjou's bike as he was asked to do, but he is having some trouble with it. Tadokoro and Makishima tell Koga that, with Kinjou injured, there is no chance of victory the next day. Koga desperately wants to fix Kinjou's bike, but Tadokoro angrily says he doesn't have to.
Teshima enters the tent with a report about Kinjou's condition. He says that the hospital confirmed that Kinjou has broken ribs and that Kinjou cannot participate in the next day's race. Koga speaks up to say that he will take on the ace's role in Kinjou's absence, but Tadokoro interrupts him by saying that they should rest. Afterwards, Koga speaks to Teshima and Aoyagi. Koga tells them about his intention to act as the ace because Kinjou has supported him all this time. He thinks that, since he is just a first year, other teams won't think to mark him. He plans to stage a comeback and seize victory for the team.
Teshima discourages Koga from trying to enact his plan. He says that Koga should focus on supporting the upperclassmen instead. Koga is disappointed because he thought Teshima would understand, but Teshima retorts that Koga has already injured his leg, so what can he hope to do? Teshima goes on to mention that Kinjou said Koga shouldn't push himself too hard, but instead use this Inter High to gain experience for next year. The two continue their argument, and Teshima thinks to himself that he is actually jealous of Koga's talent. Koga tells Teshima and a worried Aoyagi not to worry because his injury has already healed.
The next day, Koga speeds ahead of the pack as he planned, leaving Tadokoro and Makishima behind. It is clear that Koga admires Kinjou a lot, and wants to live up to his expectations. Even though Koga appears to be having trouble with his supposedly healed leg, he still pushes himself, and ends up not noticing an upcoming curve. Koga takes a serious fall down the hill that forms the curve, injuring his shoulder badly in the process. Some spectators see the accident and rush to check to see if he is all right and call for help.
Teshima and Aoyagi hear about the accident back in one of the tents where they were waiting to hand off supplies to their teammates. They both seem horrified, and Teshima looks at the supplies prepared for Koga and questions why Koga would do such a thing.
Incoming 41st Inter High Events
Building Sohoku's Cycling Team
In the manga, Koga advises Onoda Sakamichi against trying to ride rollers for the first time, and is surprised when Onoda manages to ride the rollers fairly easily.
First-Year Welcome Race
They're followed by Aoyagi in the anime instead.
In the manga, Koga is paired with Sugimoto Terufumi and introduces himself in a friendly manner. Sugimoto mistakenly thinks the practice is about building the new first-years' confidence but quickly realizes that it's in fact to show the new members their weakness. Sugimoto returns to the club room to exclaim how amazing Koga is.
Sugimoto is paired up with Teshima Junta in the anime instead.
After the 41st Inter High
Koga gets a phone call from Kanzaki Tooji saying that Sohoku's Team won the Inter High and all the members did well, the racing team by winning it and the support team that helped behind the scenes. Kanzaki also praises Koga for his help by reinforcing everyone's bikes perfectly before they left, despite staying at school due to his superstition. Koga cries and say that was about all he could do and that he was really glad.
Incoming 42nd Inter High Events
Building Sohoku's Cycling Team
Koga threatens to replace Teshima Junta on the Inter High team. It is revealed that he participated in the Inter High as a first-year even when he only rode 980km of the 1000m in training camp, but ended up crashing badly. With both he and Kinjou retiring, team Sohoku lost its chance at victory. Also, due to the injury he sustained, Koga lost his chance at returning to training camp, let alone competing as a second-year. It actually cost him 1.5 years (18 months).
Koga is comparable to Imaizumi Shunsuke and Naruko Shoukichi in that he is seen as a "elite," and he looks down on Teshima, who is just an ordinary person. Despite this apparent difference in skill, Teshima manages to beat Koga and protect his spot on the Inter High team. Afterwards, Koga reconciles with Teshima and Aoyagi, though he is of course upset that he lost his final chance at redeeming himself in the Inter High. Despite being upset over losing, Koga notices that Kaburagi Issa is suited to being a sprinter rather than an all-rounder. He tells the others about his discovery, but doesn't actually mention it to Kaburagi.
Prior to Inter High
He revealed in team meeting at his apartment that he rode the entire course by himself, albeit at slower speeds for reconnaissance, which is an important task that a third-year non-captain must perform, as Makishima did it last year. Teshima was absent as he must attend a pep rally with Mr. Pierre and the soccer team on the same day.
While the support team members were moving on the van to give the Inter High Team supplies at the supply spot, Koga decided to stay behind and check something. On the race he finds Kaburagi Issa tired and frozen in the middle of the race. He then encouraged Kaburagi to keep going and started to legally push him as he was about to retire.