Horiguchi Genki, a boy, was five years old. He was reared only by his father after his mother passed away while he was a baby. His father, Shark Horiguchi, was a professional boxer before becoming an itinerant fighter due to financial disaster. Genki had an ambition to be as powerful a boxer as his father because he thought his father was strong and would win a championship. He was adopted by his grandparents after the passing of his father. Genki decided to become a boxer despite their opposition, so he kept training covertly. He became a boxer after meeting a variety of individuals, including Mishima, the high school boxing champion, and Teacher Ashikiwa, who resembled his mother.