Demura was born on September 15, 1938, in Yokohama, Japan. At the age of 9 (1947/48), he began training in karate and kendo under an instructor named Asano. At the age of 12 (1950/51) he started training under Ryusho Sakagami in Itosu-kai karate. Demura received his 1st dan black belt in 1956, and won the East Japan Championships in 1957.
