Noriyuki Amakusa is the longtime coach and friend of protagonist Jotaro Aragaki. He advises Jotaro to retire from gymnastics due to a persistent shoulder injury and age-related decline, demonstrating his practical approach to athletic careers. This recommendation stems from concern for Jotaro's wellbeing during the athlete's prolonged slump.

Amakusa exhibits a protective nature toward those he guides, prioritizing their long-term welfare over short-term ambitions. His coaching relationship with Jotaro extends beyond professional duty, reflecting deep personal investment in his friend's future. Though reserved in expressing vulnerability, he maintains emotional awareness of others' struggles. His guardedness occasionally creates interpersonal distance, yet he consistently acts from loyalty to his athletes.

He shows resilience by supporting Jotaro's unexpected decision to continue competing despite earlier advocating retirement. This shift highlights his adaptability as a coach committed to his athlete's choices.