Warning!! Proceed with caution!!
Part of the following is not yet in the anime. If you're not reading the manga, be careful.
Touichirou Izumida[]
Last year, Touichirou invited Masakiyo to ride together when he noticed his problem with holding back his violent personality. He encouraged Masakiyo to channel his inner strength and concentrate on releasing it in the race. Touichirou tells Yukinari Kuroda that Masakiyo has an even greater transformation than he does when he sends Masakiyo out to take the sprinter checkpoint. As a fellow sprinter and someone who had the same experience of pulling the team during his second year, Touichirou is aware of Masakiyo's feeling as he pulls the team during the third day and tells Yukinari to let him expend all his energy until he retires.
Issa Kaburagi[]
At first, Issa and Masakiyo's had a turbulent first meeting. Issa was experiencing stress-related stomach pains before his debut Inter High, so he searched for a toilet. Unfortunately for him, there were no open toilets. He desperately pounded on the door to an occupied stall, greatly annoying the person inside, who happened to be Masakiyo. When Masakiyo exited the toilet, he confronted Issa. However, Issa was so uncomfortable at this point that he yelled at Masakiyo to let him go to the bathroom first. After relieving himself, his argument with Masakiyo continued and the Hakone's second year student did plant a seed of doubt in Issa's mind by insulting team Sohoku, saying that perhaps they are not as strong as the first year thinks. As the Inter High advanced, Masakiyo started to develop a respect for Issa and witnessed his growth by him not lauching an attack to take the sprinter's checkpoint, just so they can both pull the team to the beginning of mountain stage.
Sangaku Manami[]
Despite being on the same grade, their personalities are very different and its noted when they talk about their desires and both conflict with each other. Even with their differences, Masakiyo respects Sangaku for participating of the Inter High as during as a freshman and asks him how was to ride there. At first, Masakiyo did not get the answer he was seeking, but as he was riding at the Inter High during his second year he started to understand his teammate's words. It's noticeable that their relationship as teammates on the same grade grew over the course of time.