An inexperienced Irish squad made it three wins from three to wrap up their summer tour with another decisive win, writes John Fallon at the Ajinomoto Stadium.
Japan presented a more formidable challenge than last week but they were well short of shocking Ireland in a game played in warm conditions in Tokyo.
Ireland, having led by 28 points at the break in the first test, had to settle for a 28-8 advantage this time around against an improved but limited Japanese side.
They were fighting a losing battle the moment Garry Ringrose intercepted Amanaki Mafi’s pass to score after less than two minutes.
Then Josh van der Flier got his first Irish try to extend the lead to 14-0 after just ten minutes and while Jumpie Ogura responded with a penalty, Kieran Marmion pounced from close range to make it 21-3 after 16 minutes.
Japan pressure yielded a try for centre Kotaro Matsushima, but the reprieve was brief as Ireland pounded the home line and skipper Rhys Ruddock was credited with the pushover try which Jackson converted to leave it 28-08 at the interval.
Japan started the second more brightly but were denied a try when TMO Glenn Newman spotted a knock-on by scrum-half Yutaka Nagare before Shuhei Matsushima touched down.
Japan were much improved in every department in the second-half, willed on by the crowd of 29,354, but the Irish defence did well.
The pressure yielded a try for winger Akihito Yamada after 63 minutes to cut the gap to 28-13.
Ireland responded immediately but once more the TMO was called into action and a second try for Marmion was ruled out for a knock-on.
Marmion then departed for John Cooney to come on and become the eighth player to be capped on this tour.
Ireland wrapped up the win when Sean Reidy crossed for his first Irish try in his second international appearance.
Jackson added his fifth conversion in another flawless display from the tee.
Scorers for Japan:
Tries: Kotaro Matsushima, Akihito Yamada
Pens: Jumpei Ogura
Scorers for Ireland:
Tries: Garry Ringrose, Josh van der Flier, Kieran Marmion, Rhys Ruddock, Sean Reidy
Cons: Paddy Jackson (5)
Japan: Ryuji Noguchi (Ryosuke Yamanaka ’68); Akihito Yamada, Kotaro Matsushima, Yu Tamura, Kenki Fukuoka; Jumpei Ogura (Rikya Matsuda ’41), Yutaka Nagare (Fumiaki Tanaka ’53); Shintaro Ishihara (Keita Inagaki ’41), Yusuke Niwai (Shota Horie ’41), Takuma Asahara (Tsuyoshi Watanabe ’41); Luke Thompson, Uwe Helu (Kotaro Yatabe ’64); Michael Leitch, Shubei Matsuhashi (Yoshitaka Tokanuga ’68), Amanaki Mafi.
Ireland: Andrew Conway; Keith Earls (Tiernan O’Halloran ’58), Garry Ringrose (Rory Scannell ’79), Luke Marshall, Jacob Stockdale; Paddy Jackson, Kieran Marmion(John Cooney ’73); Cian Healy (Dave Kilcoyne ’61), James Tracy (Niall Scannell ’52), John Ryan (Andrew Porter ’61); Kieran Treadwell (James Ryan ’51), Devin Toner; Rhys Ruddock (Sean Reidy ’53-’63 HIA), Josh van der Flier (Reidy ’68), Jack Conan.
Referee: JP Doyle (England)