Known as the "Saint of the Sword" and the "Modern Miyamoto Musashi", he was held as one of the greatest traditional martial artists of the 20th century in Japan, as well as one of the most controversial figures in their community.

He put a street sign welcoming the practice of dojoyaburi, which he performed himself against other schools, and legend claims he never suffered a single loss, defeating over the years many kenjutsuka, judoka, karateka, wrestlers and practitioners of ninjutsu.

After the fight, a present French naval officer advanced on him while drawing a gun, so Kunii drew a knife in turn, preparing to die while hoping to take the Frenchman with him, but his opponent dropped the weapon and ran away.

[7] After Japan's defeat in World War II and the establishment of the Supreme Commander for the Allied Powers Douglas MacArthur on the country, Kunii was required to participate in a special challenge by Minister of State Junzo Sasamori.

Kunii fought as a kendo representative against a bayonet fighting instructor of the United States Marine Corps, each with his designated weapon, and despite being over twenty years older than his opponent, the Japanese won easily.