The Kiwis overwhelmed Japan 40 -12 in game one.
Akuila Rokolisoa opened the scoring in the first minute with a try which he converted himself and he would add another try to his tally in the second half.
Fehi Fineanganofo scored back to back tries in the first half, while Ngarohi McGarvey-Black also dotted down for two five-pointers.
They had a much tougher battle against South Africa, taking the match 17-5. Their final group match is against Ireland at Stade de France early on Friday morning NZ time.
"South Africa is a good outfit and we had to fight for that one. It makes our mindset a hell of a lot easier tomorrow and we have just got to build on what we have already established," Moses Leo told Sky Sport.
Coach Tomasi Cama was impressed with his side's first up effort against Japan but conceded it was tough against South Africa with New Zealand suffering a couple of concerning injuries.
"That's the game though. It's chaos and you've just got to deal with each moment ... there was a few dings out there to the boys but we managed to close it out. So very pleased with the day."
They next face Ireland.
The Kiwis are looking to go one better in Paris, having won silver in Tokyo in 2021.
