[1][2] Before his death, he was the only living Kodokan 10th dan (and one of only 15 to have attained this rank), having been promoted at the New Year Kagami Biraki Ceremony, 8 January 2006 along with Toshiro Daigo and Ichiro Abe.

[2][3] Ōsawa was born 6 March 1926 in Munakata Village, Inba District, Chiba Prefecture, Japan (now part of Inzai City).

[5] He was highly regarded as a Judo technician, particularly for his ashi-waza and, although a lightweight, was considered a favourite to win the All-Japan Judo Championships[6] and defeated the 1948 champion Yasuichi Matsumoto to win the Fukuoka tournament in November 1948.

[5] Osawa was a primary author of the book Kodokan Judo: A Guide to Proficiency.

[8] Osawa was considered to be one of the top technicians in Judo post World War II.