The Springboks will face Japan for the first time at next year's World Cup in England.
Japan beat Hong Kong 49-8 in Tokyo over the weekend to clinch the Asian Five Nations title and qualify for the World Cup.
They join South Africa, Scotland, Samoa and the United States in Pool B.
The Boks will face Japan in Brighton on 19 September, while their other group games are on 26 September (vs Samoa, Birmingham), 3 October (vs Scotland, Newcastle) and 7 October (vs USA, London).
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