Horiguchi Genki was a five-year-old boy. His mother died at his birth, and he was raised solely by his father. His father, Shark Horiguchi, was a professional boxer, but he was ruined and became an itinerant boxer. However, Genki believed his father was strong and would become a champion, and he dreamed of becoming a strong boxer like his father. After his father’s death, he was adopted by his grandparents. Although they opposed Genki boxing, Genki made up his mind to become a boxer and continued training secretly. Meeting various people, for example, Teacher Ashikiwa who resembles his mother, and Mishima, a high school boxing champion, he made his way to become a boxer.