After a slow start in the opening half at the end of which they led 12-3, Ireland cut loose in the second. They scored four tries in the space of eight minutes at the start of the second period and ended with a hat-trick of tries from outstanding flanker Niall Ronan each of which was converted by out-half, David McAllister.
The Japanese were particularly industrious in the opening half, and "ran around at 100 miles an hour " accoding to Irish manager David Haslett. For their part the Irish were a little hesitant and they could only manage two tries from Barry Murphy and Eugene McGovern with McAllister adding the conversion for a 12-3 interval lead.
However, the second half produced a totally different scenario. The Japanese managed to preserve their line for all of three minutes and then the Irish produced a sensational bout of flowing attacking rugby to run in four tries in just eight minutes.
The scoring burst began with a try from centre Nick McClelland in the 48th minute followed in quick succession by scores from wing John Hearty and lock Simon Crawford. There a slight lull then before Ronan completed the try tally with a hat-trick to complete a very satisfying afternoon for the Irish.
It was a win that manager David Haslett took particular delight in following the disappointing result against Argentina.
" I was really delighted for the boys after what has to be said was a hugely disappointing result against Argentina". he said. " The heads were down after that, but as I've said before they're a very resilient bunch and the performance today was an absolute credit to them."
"They were a wee bit slow getting out of the blocks but my goodness when they got going they played some fabulous rugby. Some of the stuff they put together in the second half was straight out of the top drawer."
The Irish play their final game in the competition on Sunday in Henley against Italy who defeated Canada 27-21 yesterday.
Ireland U21. 15. Tommy Bowe - Queens University14. Richard Lane - UCC13. Barry Murphy - UL Bohemians12. Nicholas McClelland - London Irish11. John Hearty - Blackrock College10. David McAllister - Terenure College9. Conor O'Loughlin - Buccaneers1. Eugene Mc Govern - Old Crescent2. Kevin Corrigan - UCD3. Jody Danagher - UL Bohemians
Replacements. 16. Declan Fitzpatrick - Belfast Harlequins17. Jason Moran - UCD18. Neil McComb - Dundee Highschool19. David Gannon - UCD20. Daragh Geraghty - UCD21. Michael Rainey - Glasgow Hawks22. Glen Telford - Instonians.