All-Japan Judo Championships
Inokuma was born in Yokosuka, Kanagawa, and took judo at age 15. He entered the Tokyo University of Education (current University of Tsukuba) and won the All-Japan Judo Championships in 1959 at only 21 years of age, to become the first student competitor to win the championship. He placed second in the All-Japan Championships in 1960 and 1961, both times losing to the future Olympic silver medalist and lifelong friend Akio Kaminaga.