Connacht sub-Academy player Sean Masterson started the clash as Connacht U19s man Corey Reid, Marist College, scored a try off the bench.
This was the fourth game for Japan during their tour of Ireland, which started with a 17-7 loss to the Munster Under-19s at Thomond Park on March 15. However, they subsequently defeated Connacht U19s (24-10) and Ulster U19s (20-5) in Galway and Belfast respectively.
The Japanese U19 selection had a chance to open the scoring against Ireland but their full-back Kyohei Yamasawa was off target with a long range fifth-minute penalty and the Kieran Campbell-coached hosts soon took the lead.
A fast-paced move by Ireland forced the Japanese on the back foot, and quick offloads by James Hume and Conor Wharton put St. Andrew's winger Peter Sullivan over for a try on the left. Fresh from his Leinster Schools Senior Cup success with Belvedere College, Hugh O'Sullivan was wide of the mark with the conversion.
Ireland built patiently inside the Japan 22 for their second try in the 11th minute, a slick pass by Garryowen's David McCarthy provided the platform for Sullivan to race over for his second score of the day. Out-half O'Sullivan converted for 12-0 and although there was still a lot of rugby left to play, the home side were looking extremely sharp on the 4G surface.
The Japanese also showed signs of genuine quality in possession, and they worked their way back into contention after the opening quarter had elapsed. They spread the ball wide and Yamasawa was in the right place to break over the whitewash under pressure from the retreating Irish defence.
He converted his own five-pointer before Ireland responded with another superb team try from the restart. Flanker Aaron Hall was on hand to apply the finishing touches to an enterprising attack, and a confident O'Sullivan once again converted.
In front of an enthusiastic crowd, the Ireland U19s were playing an expansive style that perfectly suited the sunny conditions, and RBAI's Hume drove over from a central position for Ireland's fourth try of the contest. After the dependable Yamasawa clipped over a penalty, Ireland took a commanding 26-10 lead into the interval.
Campbell's charges were eager to maintain their momentum, and the excellent Sullivan claimed his hat-trick at the end of a lung-bursting sprint which saw Ireland start the second period with a bang.
Nonetheless, Japan were determined to make the most of their final tour match and they responded with their second try, loosehead prop Gaku Shimizu using all of his physical power to ground the ball under the posts, and Yamasawa's second successful conversion followed.
Ireland were generally able to prevent Japan from developing any consistent pattern of play, though, and Hume completed another quick-witted move for his second try on 49 minutes.
Hiroto Mamada and Fifita Siosaia combined to set up Japanese replacement Tomoya Kimura for a try on the right flank. This converted effort brought the gap back down to a manageable 14 points, but Ireland were hell bent on finishing the game in a positive frame of mind.
Winger Mark Keane dotted down after racing onto a kick through on the hour mark, and this was supplemented by a seventh try after 68 minutes by Marist College's Reid, who was assisted by replacement scrum half James Kenny.
Japan brought the scoring to an end when winger Yoshiyuki Koga cut across from his own wing to score in the right corner, but even though Yamasawa superbly split the posts with his final kick of the day, Ireland had 19 points to spare at the final whistle.
Referee: Calum Howard (England)