Tokyo- New Zealand-born Male Sa'u ran in a try midway through the second half on Saturday to lead Japan to a 26-23 win over Italy for its tenth straight test-match win.
Sa'u's converted try gave Japan a 26-16 lead at the Prince Chichibu memorial ground. Robert Barbieri crossed for Italy's only try late to cut the deficit to three but the visitors ran out of time.
Ayumu Goromaru accounted for 14 points for Japan with four penalties and a conversion.
Saturday's encounter was Japan's only game against a Six Nations side before the 2015 Rugby World Cup where Japan will compete in Pool B against South Africa, Scotland, the United States and Samoa.