Yasutomo Arakita's promising middle school baseball career as a talented pitcher ended abruptly during his second year due to an elbow injury, shattering his prefectural tournament debut. After recovery, diminished performance and teammate mockery fostered deep cynicism. He deliberately chose Hakone Academy for its lack of a baseball club. His volatile anger dominated his first year, leading to isolation and rejection of friendships. A pivotal encounter saw him lash out at Juichi Fukutomi, insulting him and knocking over his bicycle. Fukutomi challenged him to a race—Arakita's moped versus Fukutomi's bicycle. Confident of victory, Arakita suffered a decisive loss that shattered his worldview.
Frustrated, Arakita repeatedly attempted to secretly ride Fukutomi's bicycle at night, failing each time. Confronted by Fukutomi, he was advised to "look forward" and abandon past ties. Fukutomi offered a choice: return the bicycle or join the cycling club. Symbolically cutting off his pompadour, Arakita joined. Initial training confined him to indoor rollers for two hours daily on a heavy borrowed bike. His aggressive demeanor caused unpopularity, and he frequently exhausted himself in physical confrontations. When asked his motivation for cycling, he stated it was to "prove that he existed as himself," revealing his internal identity struggle. Shinkai Hayato noted Fukutomi favored strong wills, leaving Arakita confused about being "liked".
His first race ended in collapse from exhaustion after reaching Fukutomi with no questions. During the Manazuru Circuit race, Arakita fiercely defended Fukutomi against mocking seniors. Riding Fukutomi's bike—later gifted to him—he followed orders to stay behind until the final stretch, where he sprinted to victory. This solidified his partnership with Fukutomi, whom he began calling "Fuku-chan" instead of "Iron Mask." Arakita acknowledged his success relied on Fukutomi's guidance.
By his third year, Arakita served as Fukutomi's primary assist. At the Inter High, he showed tactical awareness, dismissing claims about Sohoku's second climber until Onoda Sakamichi's arrival. In Day 1's final kilometers, he rode with extreme aggression, scraping guardrails and slamming pedals into the road. He rejected spectator encouragement, believing only self-earned effort mattered, and declared Fukutomi the sole person he acknowledged. Taunting Imaizumi Shunsuke as too conventional, he was forced into a neck-and-neck battle by Imaizumi's aggressive surge. Exhaustion prevented Arakita from countering Midousuji Akira's final attack, resulting in a three-way tie.
Post-Inter High, Arakita joined a third-year theme park trip proposed by Toudou Jinpachi. Initially disinterested, he agreed upon learning it honored Fukutomi. Despite the park's disappointing state, he remained committed to the gesture.
Arakita retains a volatile exterior, often shouting and complaining, but shows fierce loyalty to those he respects, assigning playful nicknames like "Fuku-chan" or "Onoda-chan." His baseball background fuels a competitive drive. He possesses a unique ability to "smell" others' potential or personality traits, such as work ethic or pride. He regularly feeds a neighborhood cat, causing its weight gain. Post-graduation, he attends Yonan University instead of Meisou University (where Fukutomi and Shinkai enrolled) due to program availability, passing the entrance exam without recommendation. He is susceptible to cold, fears eyedrops and roller coasters, takes academic shortcuts, and named his Bianchi bicycle "Bian."
His cycling techniques include riding at dangerous angles, striking pedals against the ground, and exploiting gaps in rider formations. His sole documented pre-series achievement is first place in the Manazuru Circuit Road Race two years prior.