Ireland have scored seven tries to overpower Japan 50-22 in a Test featuring two teams who will meet in the group stage of the 2019 Rugby World Cup.
Keith Earls scored Ireland's first try on on Saturday in the 11th minute and, with Heiichiro Ito in the sin bin, the visitors added 21 points from two tries by Dan Leavy and another by Jack Conan for a 31-3 lead at halftime.
Ireland kept the pressure on after the break with Conan crossing for his second try, converted by Paddy Jackson, for a 38-3 lead.
Andrew Conway was sent off for a high tackle in the 51st minute, and Ryuji Noguchi crossed for Japan's first try on the hour mark to cut the lead to 38-10.
Garry Ringrose and Earls added late tries before Kenki Fukuoka and Yutaka Nagare crossed to give the hosts a boost heading into the 2nd and final Test on June 24.
