Miyahara is a petite girl with large glasses who keeps her hair pulled into twin-tails.
Miyahara seems to fit her nickname of "class rep," at least when it comes to Manami, as she is very adamant about getting him to come to school on time and do his work. She even helped Manami talk to a teacher so he wouldn't have to repeat a year. Her serious personality causes her to become frustrated over Manami, who prefers avoiding work.
Manami calls his childhood friend Miyahara "Iinchou" (Class Rep.). She lives next door to him and is the one who introduced Manami to cycling when they were younger because she thought he should do more than stay in bed and play video games. Manami was previously bedridden due to sickness, but he fell in love with how cycling made him feel like he was truly alive after Miyahara brought him riding with her. Later, Manami asked for her assistance with studying for the entrance exam to Hakone Academy, where he was intending to go, because he heard of the strong cycling team. As they grew older, Manami's passion for cycling deepened, and he usually tries to avoid Miyahara's attempts to make him take responsibility for his schoolwork, opting to cycle instead. Despite her constant nagging, she cares for him, and cheers him on at his debut Inter High. She is implied to have romantic feelings for him, as she is flustered when Onoda's mother comments on her crush while spectating the race; however, it is unknown if he reciprocates or is even aware of her feelings.
- Miyahara's first name is currently unknown, but has been planned to be revealed at the 42nd Summer Inter High.
- She has a pet bird.