Japan's forward line put in a dynamic performance as rugby's Asian champions extended their record winning streak to 10 games with a nailbiting 26-23 victory over Italy on Saturday.
Male Sau's bulldozing try on the hour mark ultimately proved the difference for Japan but the home side had to survive a nervous finish before recording their first win in six meetings with the Azzurri.
"The great thing today was we won," Japanese and former Wallaby coach Eddie Jones said. "We didn't play well but it's a testament to the guys that we're beginning to win when things are not going well for us."
Japan struggled in the lineout but punched above their weight in the scrum, while Italian coach Jacques Brunel slammed his butter-fingered players as the Six Nations side lost their ninth straight game.
"We made way too many mistakes. We gave away too many penalties and committed 12 turnovers - you can't beat a team like Japan if you play like that."
Japan are set to break into the world's top 10 for the first time, but Jones insists all that matters is next year's World Cup.
"That's all I'm worried about. We've got to keep winning but we've got to win at the World Cup.
"It's no use winning up to the World Cup and not winning once you get there - like the (Japan) soccer team.
"I want to make the quarter-finals of the World Cup and become the most popular sports team in Japan. There's no reason why we can't."
Japan are in Pool B at the World Cup in England, alongside South Africa, Scotland, Samoa and the United States.
They disappointed at the 2011 World Cup under former All Black John Kirwan, beaten by hosts New Zealand, France and Tonga before drawing with Canada.
Fullback Ayumu Goromaru kicked 16 points for Japan who had beaten the USA 37-29 away last weekend.
Akihito Yamada's fifth-minute try gave Japan the early initiative until a penalty try awarded after the winger's knock-on gave Italy a foothold, the first half ending 13-13.
Italy's resistance appeared to crack when Sau crashed over in the 60th minute, but a breakaway try from Robert Barbieri made for a cliffhanging final five minutes.
Italian captain Quintin Geldenhuys paid tribute to Japan.
"All credit to them. They are a completely different team from the one we played three years ago. They've improved a lot in all phases. Now they're playing in the men's league."
