When Makishima and Toudou first met in a race, Toudou thought little of a team he'd never heard of, and tried to brag about his own fame, but Makishima just dismissed him by commenting how headbands were uncool, showing little interest in Toudou's vanity by further dismissing his insult of "beetle" (because of Makishima's unusual hair) by correcting it to "spider". During the race, Toudou became amazed by Makishima's odd cycling. After losing to him, a frustrated Toudou told Makishima that a winner should smile and the subsequent attempt was only creepy, so Toudou sought to teach him to smile properly.
The two have been rivals ever since, earning each other's respect (Makishima the new affectionate nickname of "Maki-chan".), and competing against each other in various official and unofficial races; their rivalry persists into into non-cycling activities such as ping-pong, withstanding high temperatures, and fashion as they're both fiercely competitive. After their would-be tie-breaker race only left Makishima with punctured tires before the goal and an easy win for Toudou, the two promised that they would settle the score properly at the Inter High. Up until the promised race, Toudou calls Makishima several times a day to check on his condition, as Toudou views them as "best rivals": best friends that should take care of each other, but also who can force each other to grow stronger through constant challenging, not enemies. He wishes this could continue after the Inter High.
Makishima sometimes appears exasperated by these phone calls, but he usually answers them, and Toudou is always happy to speak with him. It's such a normal occurrence that at one point, Makishima panics when he mysteriously doesn't receive any phone calls. Toudou considers their rivalry responsible for who he is as a person and how strong he's become, and feels grateful to Makishima's very existence. Makishima thinks of Toudou as "a good rival" and his equal. At the end of the The Movie, Toudou gives his bouquet for winning the mountain stage of Day 1 to Makishima.
True to his vain demeanor, Toudou often accuses Manami of having a style that overlaps with his, as well as of competing with him for fangirls. (Apparently he thinks Manami looks cool.) However, as a fellow climber and his senior, he cares for Manami and takes it upon himself to mentor him; he seems to understand Manami's need to ignore club obligations in order to ride slopes alone and doesn't get as annoyed with him as other members. Toudou himself is willing to disregard plans and advise Manami to "ride freely" if given the chance on the last day of the Inter High. Manami respects Toudou deeply for his strategic foresight in cycling, claiming to be no match for him, that he could even fall for Toudou, and accepting the advice he dispenses. He also told Manami to stop blaming himself for helping Onoda when they first met and in turn helping Onoda beat him at Inter High, and helping him learn to be gracious, be it a winner or loser. It also had to do with the fact that Toudou lost his frenemy: Makishima
Initially, Arakita didn't get along well with Toudou in the slightest. After Toudou tried to be friendly when Arakita first joined the club, Arakita simply insulted his hairstyle and refused to tell Toudou about his past athletic experience, which Toudou could tell must have existed. Although he instantly understood Arakita probably had bad memories about his past, Toudou was insulted by the headband comment to the point that he wanted Arakita to quit the club. Over time, though Toudou claims he never thought they'd be riding together, the two grew to highly respect each other as cyclists. As third years, they tend to bicker, but usually over trivial things like Toudou scolding Arakita for trying to copy homework or his eating of unhealthy food, and when Arakita insults Toudou for not knowing something, Toudou is quick to study up on it out of spite. When Arakita dropped out before Day 3's Sprinter's Checkpoint of Inter High, Toudou and the team spoke highly of him. They seem friendly enough towards each other regardless of how they clash; In extra material, Arakita has called Toudou to wish him happy birthday and offered to buy him a soda. (Unfortunately, he mistakenly called someone else.) Watanabe said that Arakita would be the first to text Toudou "Happy Birthday" despite how he acts, because that's the sort of guy he is. At one point, Toudou, after Arakita berates him for being terrible at handling cats, doesn't hesitate to cuddle Arakita like a cat to demonstrate his newly-learned cat appreciation techniques.
As teammates, Shinkai and Toudou are on amicable terms. Toudou is aware of the fact that Shinkai is his "rival" (and perhaps even equal) in popularity, particularly in regards to girls. Shinkai does not seem to care about getting attention from spectators, and at times doesn't even seem to notice it, a fact that great irritates Toudou.
As captain and vice-captain, Fukutomi and Toudou are on good terms. Notably, Toudou calls Fukutomi by the nickname of "Fuku" (and on one occasion, "Tomi").
Shuusaku was a childhood friend who encouraged Toudou to enter the world of road racing during their eighth grade year when he convinced Toudou to join him in the Hakone Road Hill Climb. Toudou's fixation with fashion and appearances, as well as his confidence and aloofness, frequently baffled and amazed Shuusaku. Since Toudou used his white Ridley to win the race, it can be speculated that the white Ridley Toudou rides during the 41st Summer Inter High is the same one Shuusaku gave him, or at least inspired by Shuusaku's.
Minami, along with Shuusaku, was the one who encouraged Toudou to race for the sake of winning the Mountain Prize and red number tags, and to join Hakone Academy, sparking his career as a climber. She was also the one who caused his signature headband style.