Ohsaki Sensei was born in 1948 in the Shibuya section of Tokyo. He was interested in budo as a child, and at the age of seven he began to study Kodokan judo. His instruction began at the Hatagaya Keisatsu Dojo, one of the numerous dojo sponsored by the Tokyo police department. These keisatsu dojo, or police dojo, are infamous throughout Japan for the severity of their training. His initial training began with soji, the ritualistic cleaning of the dojo. For some time, he was only allowed to clean and watch his sempai (seniors) practice. Eventually, having proven his sincerity, he began learning safe falling techniques (ukemi) and later throwing and grappling methods.

In time, he completed college, became an automotive technician, married, and had two sons, one of whom has trained for many years in kyudo (the martial art of Japanese archery). He is presently the owner of an automobile repair facility. His judo training continued successfully throughout most of his life.

Eventually, Ohsaki Sensei also began a comprehensive study of traditional jujutsu and classical Japanese weaponry, which he has excelled in for many years. A member of the Kokusai Budoin's prestigious kobudo, or ancient martial arts, division, he has demonstrated Nippon jujutsu at the Kokusai Budoin Sogo Budo Taikai. This important budo exhibition takes place early each spring at Otakumin Plaza in Tokyo. (Japan's Kokusai Budoin promotes all traditional Japanese forms of budo and bujutsu, and it is active in a large number of countries throughout the world.) Besides budo, Ohsaki Sensei has extensive training in Japanese forms of meditation and healing arts, along with a comprehensive background in shodo, the art of Japanese calligraphy.