Despite spending much of his career in the shadow of Daisuke Ohata he is considered an all-time great of Japanese rugby in his own right.
Onozawa made his debut for Japan against Wales in June 2001 and immediately impressed troubling the Welsh defence throughout and scored a try from 75 metres out from a move that he started himself.
[2] In the 2007 Rugby World Cup, Onozawa again played in all Japan's matches and notably scored a 70-metre individual try against Wales.
[4] Onozawa was retained by new coach Eddie Jones, and 2012 proved to be one of his most successful years at age 34, becoming the 5th player to score 50 international tries in May 2012 Hong Kong, and overall scoring 10 tries in 8 matches, including tries in Japan's first ever wins away in Europe against Romania and Georgia in November.
At domestic level, Onozawa played for 14 years with Suntory Sungoliath, before joining Canon Eagles in 2014 to finish his career.