Aoyagi met Teshima Junta on their first day at Sohoku High School. Teshima saw him tiredly riding his road racer up the front gate's slope and became intrigued. Teshima approached Aoyagi as he was locking his bike afterward and introduced himself. Aoyagi, although sounding shy and quiet, returned the introduction and said his name "Hajime" was written with the symbol for "first". (一) This made Teshima smile; he felt a kinship with him as fellow average cyclists. Teshima spoke to him at lunch about how 一 must mean victory, as in victory for first place in races. Although Aoyagi didn't speak much, Teshima felt he was aiming for the same "elite" world as he once was. Both of them were in the same class together (1-4) and joined Sohoku's bicycle club together, as Aoyagi inspired something in Teshima to continue cycling.
During the training camp to select Inter High members, Aoyagi placed ahead of Teshima, who placed last, but he still did not do well. It's implied due to the lack of other cyclists around them that Aoyagi may have ended up in second-to-last place. However, the second-year Tadokoro Jin comforted Aoyagi and told him he had the right idea, but needed to better manage his pace and account for the amount of distance he had to cover while cycling. Aoyagi started bonding with Tadokoro. Upon hearing they weren't going to the 40th Summer Inter High from Kinjou Shingo, Aoyagi had no response, while Teshima suppressed his feelings, as it wasn't unexpected to him that "ordinary" cyclists like them lost. Aoyagi went with Teshima to see the Inter High first-hand, and this changed Teshima's resolve entirely. Later, he emotionally ranted to Aoyagi about his desire to ride in the next Inter High.
Aoyagi quietly listened, and upon hearing Teshima speak of his limits riding alone, suggested they turn "one" into "two": that they ride as a "team of two". Teshima accepted this idea and they shook hands, practicing together from that day onward, developing their skills and strategies. Aoyagi acted as the legs to win while Teshima was the brains of the team that managed Aoyagi's stamina. This earned them five wins in six races during their time as first-years. Although Aoyagi would apologize to Teshima for being the only victor, Teshima felt they'd won together and was satisfied beating "elite" cyclists this way.
After joining Sohoku's cycling club, Teshima was also mentored by Tadokoro along with Aoyagi, and he also became specialized in knowing what Aoyagi was thinking to almost psychic levels. They wore a special set of cycling gloves: Teshima wore a glove with "certain" written on it, while Aoyagi wore a glove with "victory" written on it.
Building Sohoku's Cycling Team
Aoyagi and Teshima keep their pace relatively slow until the first-years catch up with them. As they planned beforehand, Teshima sends Aoyagi ahead and tells the first-years that they're going to play a game of tag to see if they can catch Aoyagi. Aoyagi, after riding around the track once and catching up, finds that the three first-years have managed to pass Teshima. Aoyagi tells Teshima that it is meaningless if they don't succeed together and reminds him of their desire to go to the Inter High with Tadokoro. Aoyagi's words lift Teshima's spirits and the two catch up to compete with the first-years. They needed to reach the goal before the first-years because, if they did, the first-years would be bound by the "no overtaking" rule put in place at night. Despite how hard he and Teshima tried, they lose to the first-year trio. Afterwards, it is shown that he and Teshima both strained themselves so much during this event that they had to drop out of the camp. Teshima tells the first-years that they need to win the Inter High for them and for the team, and Aoyagi seems to share this sentiment.
During the Inter High, Aoyagi supports all of Sohoku by giving them their supplies as they pass by. He was there when Onoda and Tadokoro fell behind, and he encouraged them to continue along with Teshima.
After the Inter High
After the Hakone Academy third-years have completed their day at a theme park, they look over the photos taken earlier and are startled to see Onoda and Imaizumi racing on children's bikes in the background of one. Behind them, team Sohoku (minus Makishima. but including Aoyagi and Teshima) rides on a multi-person bike, with Kinjou running behind them, shouting about how Sohoku never gives up.