Demura was born on September 15, 1938, in Yokohama, Japan. At the age of 9, he began training in karate and kendo under an instructor named Asano. At the age of 12 he started training under Ryusho Sakagami in Itosu-kai karate. Demura received his 1st danblack belt in 1956, and won the East Japan Championships in 1957. In 1959, he began training in kobudo, a style of Okinawan weapons training, under the direction of Taira Shinken. In 1963, he "came to know the Koga Ryu Ninjutsu Soke, Seiko Fujita- a 14th Generation Koga Ryu Ninja - personally". Demura met martial arts scholar Donn Draeger, who introduced him to Dan Ivan, who would eventually bring him to the United States of America as a karate instructor.
In 1965, Demura came to the United States, representing the Japan Karate-do Itosu-kai. From his base in southern California, he became well known for his karate and kobudo skills. In 1971, he was ranked 5th dan, and he remained at that rank until at least 1982. Through the 1970s and 1980s, Demura wrote several martial arts books, including: Shito-Ryu Karate, Advanced nunchaku, Tonfa: Karate weapon of self-defense, Nunchaku: Karate weapon of self-defense, Bo: Karate weapon of self-defense, and Sai: Karate weapon of self-defense. In the 1980s, Demura became involved in the Karate Kid series of films. He was the stunt double for Pat Morita, who played Mr. Miyagi. Demura has appeared in several films and documentaries, including: The Warrior within, The Island of Dr. Moreau, The Karate Kid, The Karate Kid Part III, Shootfighter: Fight to the death, Rising Sun, The Next Karate Kid, Masters of the martial arts, Mystic origins of the martial arts, Modern warriors, XMA: Xtreme Martial Arts, and Ninja. Demura is the subject of the 2015 documentary "The Real Miyagi". In 1986, Demura was promoted to 7th dan in Shito-ryū karate. In 2001, he was expelled from the Itosu-kai, and became the Director of Shito-ryū Karate-do Genbu-kai. In 2005, he was promoted to 9th dan. He currently resides in Santa Ana, California. In October 2010, Demura performed for the United States Martial Arts Festival, hosted by Koyamada International Foundation at the Redondo BeachPerforming Arts Center in Redondo Beach, California.
