An absorbing tussle at Tokyo Stadium was only one-sided in the closing minutes as South Africa pulled away to win 26-3 and set up a semi-final against Wales next Sunday.
It was not to be though, with South Africa's resolute defence repelling the threat of Japan's scintillating backs.
The Japanese team had been ranked sixth after advancing to the knockout stage for the first time.More news: Crystal Palace vs. Manchester City - Football Match Report
"I'm disappointed for the players because they give so much to the group and they gave so much to the country in this World Cup".
But fleet-footed Japan, dominating possession, were soon giving South Africa the run-around and Tamura got them on the board at 3-5 down after a surprising scrum penalty against the heavyweight Springboks pack.
Man of the match Faf de Klerk, who had helmed the South Africans artfully throughout, added a second try on 66 minutes and Mapimpi added his second four minutes later.More news: Emilia Clarke Felt 'Heartbreak' Over 'Game of Thrones' Finale
"And I have to thank the fans - we wouldn't be here if we didn't have the support of the whole country". Wales defeated France 20-19 on Sunday.
France were leading 19-10 when lock Sebastien Vahaamahina, in a moment of madness, inexplicably elbowed Aaron Wainwright's in the face and was shown a straight red.
Though the French defended superbly, replacement number eight Moriarty, yellow-carded himself earlier, clinched the encounter six minutes from time by grabbing a loose ball and forcing his way over.More news: Boris Johnson battles to save Brexit deal
Sunday's results completed the semi-finals line-up for next weekend, after defending champions New Zealand brushed aside Ireland to go on a collision course with England, who convincingly beat Australia.