(from ebookjapan):

Moka, Tochigi Prefecture, 1931. When Yujiro Watanabe, founder of the Japan Kenpo Club, visited Moka for a boxing match, a young boy jumped in to challenge Hanai, a professional boxer, and almost won. He was Tsuneo Horiguchi, captain of the Moka Junior High School Judo Club.

Horiguchi went on to attend Waseda University, where he was welcomed into the Japan Kenpo Club by Watanabe, who saw in him a great talent. Horiguchi, who was devoted to a unique style that disregarded defense and just kept on hitting, participated in the Japan-France Kenpo tournament for the Japanese selection.

His fighting style earned him the nickname "Piston". After advancing to the finals, Horiguchi faced his senpai, Kaneo Nakamura, who was known as a "knockout artist," and won. And so to the French-Japanese duel!　

This is the first work by Kajiwara Ikki and his last work. Behold the origin of Kajiwara's world!

What the last sentence refers to is the manga being an adaptation of a short story (not a manga) that Kajiwara wrote in 1959, entitled Make Him Strike, and I Shoot (打たせて撃つ, Utasete Utsu), serving as his debut work. It is also his last as the manga was done in 1986, one year before his passing.