Naruko met Onoda during his first visit to Akihabara. Naruko immediately recognizes Onoda as an otaku and asks him for advice about what figures to purchase. However, he ignores Onoda's advice and buys the figure that looks the coolest, which put 1000 yen short and so he asks Onoda for a loan (which he only returned with a candy in Omake 4). Once they leave the store, Onoda thinks that Naruko is the kind of friend he would like to go to Akihabara with, although initially Naruko keeps mispronouncing his name as Onoda couldn't speak to him properly at first. Later, a man insults Onoda's city bike and Naruko convinces Onoda to chase the man down together on their bikes by riding quickly on the road - something Onoda had never done before. Naruko also taught him how to use his new front deraileurs to shift gears, and he was surprised by Onoda's speed. This is the first time that Onoda rode cooperatively with another cyclist when Naruko pulled for him, then pushed him to get to the car. But while Onoda overtook the car, he forgot to return the cigarette butt. Afterwards, like Imaizumi, Naruko suggests that Onoda should join the cycling club. As the series progresses, they become incredibly close friends and Naruko ends up as something like a brother figure to Onoda.
Naruko and Imaizumi have a relationship as rivals. They are often seen competing in and outside of club activities, as Naruko already built his reputation in Kansai Prefecture by competing in many sprint races. The two have also been referred to as a "duo", nicknamed "the redhead and the giant" by other students in the school. Initially, Imaizumi and Naruko had little regard for each other, as they were too wrapped up in their individual success. As the series progresses, they are seen together more frequently and their behavior becomes more playful than truly hostile. During the Inter High, Naruko expresses the desire to win together with the team, Imaizumi included. But after losing the Sprint Checkpoint on Day 3 of Inter High, They again fought to pull for Tadokoro, but ended up pulling together instead, much to Tadokoro's amazement and amusement.
After the first Inter High, Imaizumi approaches Naruko with a proposal: Naruko should become an all-rounder too. Imaizumi says that the current team, without the strength of the graduated third years, cannot win the Inter High. He notes that Naruko has exhibited the potential to be a talented climber as well as sprinter, and should therefore become an all-rounder like him. Naruko is offended by this suggestion, as he is very proud of being a sprinter, but also seems to be a bit pleased that Imaizumi thinks he has the capability to become an all-rounder. After returning home to Osaka and losing to Midousuji, consequently being forced to give up his title as a sprinter due to a bet of his own design, Naruko decides to accept Imaizumi's offer, but he refuses to become an assistant.
Tadokoro acts as a mentor to Naruko, and Naruko often challenges Tadokoro and tries to prove that he can be faster than Tadokoro, but he could not do so in the Paired Race, having lost to him 2-8 having requested to repeat the race until he won. He often calls him "old man" (ossan), a nickname which Tadokoro dislikes and responds to by calling Naruko "red head." Naruko strives to become faster than Tadokoro due to his competitive nature. Tadokoro responds in kind, doing his best not to be shown up by a first-year. Naruko and Tadokoro shared stories of their past losses during the sprinter battle on the first day of the Inter High. Those losses helped them grow stronger since they had to work hard to win.
While Naruko never thought much of him before, he is always in awe of how Teshima is telepathic and able to know what Aoyagi's trying to say.
After Inter High, however, Naruko's respect for Teshima has grown immensely after seeing Teshima's race against Ashikiba in the Minegayama Hill Climb Race. After losing against Midousuji, Naruko heeds Imaizumi's advice and asks Teshima to help him become an all-rounder.
Initially, Midousuji doesn't take much notice of Naruko, until he realizes Naruko is mentally stronger than Imazumi, even when he is physically weaker and less able to keep up with him. Naruko also never falls for any of Midousuji's tricks or bluffs, something Imaizumi still does in year 2.