South Africa beat Canada, Kenya and the USA on the opening day of the Tokyo Sevens.
Seabelo Senatla scored a hat-trick against the Canadians, with Werner Kok and Kwagga Smith also crossing the line, as the Blitzboks kicked off their campaign with a 26-7 win.
South Africa then blanked Kenya 26-0 thanks to tries from Justin Geduld, Smith, Chris Dry and Rosco Speckman.
The Blitzboks made it three from three when they fought back from a 10-5 half-time deficit to beat the USA 24-15, with Cecil Afrika, Kok, Kyle Brown and Ruhan Nel scoring tries.
South Africa will now play Scotland in the Cup quarter-finals on Sunday.
With just two more tournaments to come after the Japanese event, the Blitzboks (110 points) currently have a slender two-point lead over Fiji, with New Zealand three points back. The top four teams on the final World Series standings at the end of the season in May will qualify automatically for the 2016 Olympic Games in Rio.
Sunday's Cup quarter-finals (to start 4:20am SA time):
Fiji vs Japan
South Africa vs Scotland
France vs England
New Zealand vs Canada
Photo: Chris McGrath/Getty Images