Norton-Knight was signed by Cardiff Blues from the New South Wales Waratahas at the end of the 2008-09 season and made his debut for the Blues against Edinburgh at the Cardiff City Stadium in September 2009.
His first eight appearances for the Blues were at outside half before switching to fullback for the LV Cup match against Gloucester at Kingsholm where he scored a try. He went on to make 20 appearances for the Blues, scoring three tries and a drop goal.
The Blues thanked Norton-Knight for his efforts in what was a difficult transition for him and wished him the best of luck with his onward rugby career.
Cardiff Blues CEO, Robert Norster added, "Sam is a talented athlete and rugby player that sadly we did not see fulfil his full potential here in Wales. On behalf of everyone at the Blues, I would like to wish Sam and his partner, Natalie every success and happineswith their future in Japan".