Gorō Raiden, a foundational member of Musashi Mountain High's sumo club, was recruited by founder Goshogawara alongside judo captain Kaoru Kiyokawa, pro wrestler Takayuki Kannai, and aspiring delinquent Nanno Ippei. He possesses a notably large and imposing physical stature, towering over his peers. Despite this formidable presence, he exhibits an extremely shy and reserved personality, often appearing visibly uncomfortable during social interactions.

Raiden demonstrates expertise in the strategic board game Go, indicating a capacity for deep concentration and analytical thinking. His involvement in sumo stems directly from the club's need for enough members to compete formally. During training and competitions, he contributes significant physical strength to the club, participating in matches against professional sumo wrestlers alongside his teammates. His journey reflects a transition toward being part of a cohesive athletic unit, though his inherent shyness remains constant. His participation represents a commitment to the club's objectives despite personal reservations about attention or confrontation.