Korea's duo of Meena Lee and Bo Bae Song carded one of the two bogey-free rounds on Friday to share the lead with the Swedes.
'Both of us played really well today,' Song said.
The teams will play foursomes, or alternate shot, on Saturday before finishing with stroke play on Sunday with both players score counting.
Amy Hung and Yu Ping Lin of Taiwan stand alone in third place at 5-under-par 67.
The United States tandem of Paula Creamer and Natalie Gulbis are one shot further back at minus-4 at Gary Player Country Club. Gulbis posted the lone eagle of the day when she ran home a 45-foot putt on the par-5 ninth.
The Korean team went out three groups before the Swedes and got on the board with a birdie at the second. They came right back to birdie the third as well.
After five straight pars, the Koreans birdied the ninth to turn at minus-3. Around the turn, they collected birdies at the 11 and 13, both par-4s, to climb to 5 under.
The Koreans picked up their sixth birdie at the par-5 14th. They got to 7 under as they birdied the par-3 16th before closing with a pair of pars.
'The rough was difficult and we tried to go for accuracy rather than distance off the tee,' said Lee.
The Swedes ran off three straight birdies from the third. They wrapped birdies at the seventh and ninth around a bogey on No. 8 to post 4 under on the front side.
Like their co-leaders, the Swedes birdied Nos. 11 and 13 to move to minus-6. Sorenstam drained a 9-foot birdie putt on the 16th to move into a share of the lead after the opening round.
'It was tough to keep focused because we were out there for a very long time,' said Neumann. 'Whenever we got to a tee box, the group ahead had just walked off. So it was a day spent looking for shade, but we're happy with our performance and we're obviously in a good position.'
Laurette Maritz and amateur Ashleigh Simon from the host country of South Africa posted a 3-under-par 69. They were joined in fifth place by the Finnish pair of Minea Blomqvist and Riikka Hakkarainen, Colombian sisters Marisa and Christina Baena, Paula Marti and Marta Prieto of Spain and Lynette Brooky and Gina Scott from New Zealand.
Four more teams from Wales, Canada, Scotland and Germany are one stroke further back at minus-2.
Japan's Ai Miyazato, who won last year with Rui Kitada, is defending the title with Sakura Yokomine as her partner. They struggled to a 1-over-par 73 and share 19th place with Italy.