Tokyo - Former players, fans and officials reacted with astonishment after Japan produced the shock of the World Cup to beat the highly fancied Ireland 19-12 in a result that set the tournament on fire.

Here is a round-up of some of the best reaction on social media to the "Shizuoka Shock."

- 'Didn't go to plan' -

"Well that certainly didn't go to plan. Now need 10 points from the final two pool matches and see what way the chips fall. Very disappointing after the first-up performance but massive congrats to an excellent Japan." (Ireland great Brian O'Driscoll).

- 'An absolute joy' -

"OMG (Oh my God). What have we just witnessed from @JRFURugby. An absolute joy to watch them. 12-3 down to a fine @IrishRugby side!! I think the miracle of Brighton 2015 now has a Blockbuster sequel." (Ex-England captain Lawrence Dallaglio).

- 'Ringing in my ears' -

"It is ringing in my ears now. 'We've been getting ready for this game for a year. Ireland have been getting ready since Monday'." (Former Ireland centre Gordon D'Arcy recalls Japan coach Jamie Joseph's pre-match comments).

- 'Crucial' bonus points -

"People are bagging Joey Carbery for kicking the ball out at the end. They had a bonus point. They were out on their feet. Japan were energised and the Irish had to go 95 metres to score. In that group, bonus points will be crucial and they could have easily lost theirs in forcing it." (Former England flyhalf Andy Goode)

- 'Incredible performance' -

"Congratulations Japan @JRFURugby -- worthy winners today with an incredible performance and amazing support. Thanks to our own fans who cheered us to the last -- wonderful as always." (official Irish Rugby Football Union Twitter feed).

- 'Well well well' -

"Well well well. @JRFURugby absolutely fantastic performance. Japan v @Scotlandteam now very interesting." (Wales great Jonathan Davies).

- Don't know the rules -

"I don't know rugby rules but still I am excited. Go for the next game!" (Japanese twitter user @aya_001a).

- 'I cried' -

"I watched a rugby game from the beginning to the end for the first time today and I'm extremely excited. I cried and I'm given courage," (Japanese twitter used @potapota3198).