Fly-half Jumpei Ogura kicked 18 points for Japan as they completed a 33-21 victory over Romania in Kyushu on Saturday.
Romania got off to a promising start after Florin Vlaicu kicked two penalties in the first six minutes to take them to a 0-6 lead.
Seven minutes later, Japan responded back with a touchdown from Akihito Yamada while Ogura kicked a conversion followed by three penalties before his counterpart slotted his third penalty as Brave Blossoms gained a 16-9 lead which soon became 23-9 at half time with Kenki Fukuoka strolling past the post.
The onslaught from Japan continued as flanker Michael Leitch danced past the post at the start of the second and Ogura's conversion and a penalty stretched the home side's lead to 33 points.
Just as it looked all over for Romania, centre Sione Faka'osilea showed great resilience as they scored the first try of the game following which Japan lost replacement Heiichiro Ito temporarily when he was sin-binned in the 63rd minute. Romania skipper Mihai Macovei capitalised on the advantage as his touchdown brought down the difference but could not prevent his team from succumbing to a 12 point defeat, Japan 33 - 21 Romania.
Japan will now host Ireland in a two-match Test series to be played in Shizuoka and Tokyo on 17th and 24th June, 888sport have all the live odds here.
Ireland and Leinster fly-half Joey Carbery's ankle injury will rule him out both test against the Blossoms, picking up the injury in Ireland's 55 - 19 victory against the USA Eagles.