Sean Jansen scored a try on his Ireland debut as they made it a perfect opening two wins from two in their Nations Championship campaign with a 36-20 bonus-point win over Japan in Australia.
Nick Timoney, Tom O'Toole, Robbie Henshaw and Tom Stewart were responsible for Ireland's other tries, Ciaran Frawley kicked for six points and Harry Byrne for four to ensure they remained top of the Northern Hemisphere group.
Ireland head coach Andy Farrell made nine changes from their narrow win over Australia, with Tadhg Beirne captaining for the first time and hooker Ronan Kelleher reaching a half-century of caps.
Number eight Jansen started, while his Connacht teammates Billy Bohan and Sam Illo were also handed debuts off the bench alongside Ulster back rower Bryn Ward.
It did not take long for Japan to strike, capitalising on an error-strewn Ireland lineout that allowed Taira Main to run in their first try in the third minute.
Ireland hit back six minutes later, keeping the pressure on after Henshaw took a big hit, and were rewarded when Timoney drove between the posts.
There was another poor lineout from Farrell's side before Takuro Matsunaga pulled Japan back in front with a penalty, then Ireland took the lead when O'Toole crossed the whitewash in the 20th minute, aided by Stuart McCloskey.
The lead switched again as Matsunaga added a second penalty, but it was 19-13 to Ireland after Henshaw powered over with six minutes remaining in the first half.
Illo came on for his debut in a double-change for Ireland, who started the second half more clinically as fellow replacement Bundee Aki justified his introduction, latching onto a Henshaw pass.
His run got Ireland close, but it was Jansen who finally finished the job and secured the bonus point in the 50th minute.
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Japan kept it a contest, taking advantage again after Ireland let themselves down from the lineout, paving the way for substitute hooker Hayate Era to battle his way to a try two minutes before the hour.
Byrne added a much needed cushion with a penalty to make it 20-29 with 10 minutes remaining.
Japan were reduced to 14 men when Era was sent off with three minutes remaining before Stewart, set up brilliantly by Ulster teammate Nathan Doak, sealed the win.