Yuuya Hashiba, a July 20-born sophomore at Asamizo High School with blood type O, founded and leads the school's judo club with headstrong passion. His dedication to martial arts is matched by a quick temper. Open and expressive, Yuuya stands in sharp contrast to the reserved Shinobu Oda, his romantic rival.

Eleven years before the main events, Yuuya intervened with Shinobu to protect a young Nonoka Aida from a drunk assailant wielding a broken bottle. During this rescue, Yuuya sustained a permanent forehead scar while throwing the attacker. This act made him one of Nonoka's unknown childhood saviors. Yuuya later developed romantic feelings for Nonoka, fueling a bitter rivalry with Shinobu as they competed for her affection.

Fiery and impulsive, Yuuya swears more frequently than others. He shares a polar opposite relationship with his twin brother, Masaya Hashiba, a pessimistic delinquent lacking inspiration, though both brothers exhibit a love for fighting. Yuuya occasionally switches places with Masaya, such as during Nonoka's shoulder injury rehabilitation, though Nonoka detects the ruse. After Yuuya assaulted a reporter, Masaya took the blame to shield Yuuya from tournament disqualification, demonstrating Yuuya's willingness to protect others despite consequences.

Yuuya's rivalry with Shinobu evolves significantly. Initially hostile due to conflicting judo philosophies and competition over Nonoka, their relationship transforms into grudging mutual respect. They ultimately reconcile, becoming vitriolic best buds who collaborate to train Nonoka for Olympic competition. In the OVA "Wedding★Combat," Yuuya enters a martial arts tournament to stop Nonoka's forced marriage to Hajime Ichijou. He engages Hajime in a "Cock Fight" and openly declares his protective stance toward Nonoka.

As judo club leader, Yuuya implements rigorous training, like an extreme obstacle course designed for recruitment. His unwavering commitment to judo inspires loyalty among club members despite his abrasive demeanor.