In Die Rapport newspaper and reproduced on the main South African Afrikaans news site netwerk24.com, Gert van der Westhuizen wrote a lament headlined: "The darkest day in South African history".
He compared it with the 1891 British Lions tour to South Africa where the Boks lost every test.
"South Africa lost against Japan. Not against the All Blacks. Not against the Wallabies. Not even against Argentina or Wales or England or Ireland. Against Japan. A country that 24 years ago last won a World Cup match (against Zimbabwe). A land that 20 years ago lost 17-145 against New Zealand. A land that last year still lost 21 - 61 against the New Zealand Maori (not the All Blacks). A land that is 13th on the world rankings," van der Westhuizen wrote.
"Really a land that was a joke in world rugby. A land that was made fun of over its small players and that could not even scrape together a super rugby team.
"But on Saturday, Japan was a giant.
"There can absolutely be no excuses for the defeat. It is time for South African supporters, most of all the rugby leaders and the minister of sport, to be brutally honest over their team.
"There was no plan B or creativity."
South African fan comments included the following:
* "You have already embarrassed us enough, losing against Wales, Japan and Argentina! Its absolutely shocking."
* "Congratulations to Japan, you were fantastic!"
* "Fans should have lynched him (coach Heyneke Meyer) on the field. The worst Springbok coach in the history of the game. Get (Jake) White in immediately.
* "Well done Japan, we brought the old age home to a young man's tournament."
* "Age is not an excuse. Our squad's average age is less than New Zealand. All the blame goes to Heyneke (Meyer) for this one. We were just terrible, that is all."
* "South Africa made Schoolboy errors and I think it is a dark, dark, dark, day in Springbok history."
The best of Twitter reaction:
