The Cherry Blossoms may not have made the last eight, narrowly missing out behind South Africa and Scotland in Pool B, but have won the hearts of neutral followers.
The stunning opening match victory over the mighty South African Springboks
will be long remembered for its sheer audacity, with a last-gasp try, but it has been backed up with further wins against Samoa and now the Eagles of the United States.
The only defeat came against Scotland, 45-10, as coach Eddie Jones' team was unable to back up the opening win with a short time to recover.
Returning to Gloucester's Kingsholm Stadium, Japan was able to erase the memories of that defeat by running in three tries through Kotaro Matsushima, Yoshikazu Fujita and in the second half Amanaki Mafi.
It was backed up by the ever reliable boot of Ayumu Goromaru, with two conversions and two penalties to take his tally past 50 for the competition.
The United States kept in the match through tries from Takudzwa Ngwenya and skipper Chris Wyles, but could not match the intensity of the Japanese team.
Jones, who is leaving his role after the World Cup, said the team was well placed to make an impression as hosts of the competition in 2019.
"I've done my job with Japan and that's me done. I wanted to bring back pride and I've done that," he told ITV Sport.
The crunch match of the day was a pulsating encounter in Cardiff between Ireland and France to decide who topped Pool D.
For the winners the added prize was avoiding the New Zealand All Blacks in the quarterfinals and it was the Irish who emerged victorious 24-9.
Second half tries from Rob Kearney and Conor Murray proved the difference after Ireland led 9-6 at the break.
But victory came at a heavy price with skipper Paul O'Connell, Johnny Sexton and Peter O'Mahony all going off with injuries.
The outlook for O'Connell, who is retiring at the end of the World Cup, looks particularly bleak, with coach Joe Schmidt admitting he might have played his last game for his country after being stretchered off.
Sexton's young replacement at fly half, Ian Madigan, was one of the Irish heroes after the break, finishing the match in tears at the emotion of the occasion.
It's Argentina next for Ireland in the last eight, the Pumas running in nine tries earlier Sunday to beat Namibia 64-19 in their final Pool C match.
Sunday's other match saw Italy beat Romania 32-22 in Pool D to secure automatic qualification for the 2019 competition.