Okubo played 23 matches for the Japan national rugby union team from 1999 to 2004.
[1] His regular playing positions were Flanker and Lock.
As of December 2013[update] Okubo is the coach of Top League team Suntory Sungoliath.
[2] In 2015, Okubo became the coach of NTT Communications Shining Arcs.
[3] He was named the first Non-Kiwi coach of the Sunwolves in their last year of Super Rugby in 2020.