Itokawa Shuusaku was a friend of Toudou Jinpachi during their middle school years. His family runs a bicycle shop called "Cycle Shop Itokawa." Shuusaku convinced Toudou, who was only ever concerned about fashion despite his cycling skills on a granny bike, to practice for the Hakone Road Hill Climb Race, which lead Toudou to become aggressive and disregard the status of his appearance in order to win.
Finding something in himself, Toudou joined Shuusaku at the actual race and learned about what it means to win first prize from Minami, the manager of Hakone Academy's team at the time. Shuusaku was told by Minami he'd be given a kiss if he won. Panicking at the serious look Toudou had, thinking he wanted Minami's kiss too, Shuusaku sprinted so much at the start of the race that he injured himself. Realizing Toudou simply wanted victory and recognizing his friend's potential, he gave his white Ridley to him and Toudou easily won the race with it.
→ Main article: Toudou Jinpachi's History
Shuusaku was a small boy with short, black, cropped hair that had a very sharp widow's peak; he had large blue eyes.
He seemed to be a kind boy who recognized strengths in others even if they themselves couldn't, although he was quick to jump to conclusions. He didn't like being teased about his crush on Minami, and got nervous when it seemed someone else was after her affection.
He 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.
Shuusaku knew Minami from how often she visited his family's bike shop to buy parts. He had an obvious crush on her and was excited when she said she'd give him a kiss if he won the race, and became extremely distraught when he thought Toudou was racing to win her kiss too.