Ohsaki Jun Sensei was born in the Shibuya section of Tokyo, Japan. As a child, he began to seriously study Kodokan judo, a practice which he has continued to this day. He is a judo yudansha (black belt). Ohsaki Sensei was educated in Japan, and he graduated from Nippon University with a BA in political science and law.

As a young man, Ohsaki Sensei moved to the United States, where he married and raised his children. In 1990, he began to study Japanese yoga and the martial art of aiki-jujutsu, and he has received teaching certification in both arts. Shortly after he commenced his training in Japanese yoga and aiki-jujutsu, he began to study shodo (classical brush writing) and sumi-e (ink painting) as well. Ohsaki Sensei continues to be an ardent exponent of shodo and sumi-e.

He has, furthermore, demonstrated aiki-jujutsu in Japan at the Kokusai Budoin Sogo Budo Taikai. He has also written about Shin-Shin-Toitsu-Do (Japanese yoga) for the Nichibei Times.

Ohsaki Jun Sensei lives in the San Francisco Bay Area, and he is the owner of Japan Auto, a service center for Japanese cars.