Ciaran Frawley has been handed his first Test start at fly-half as part of a new-look half-back pairing with Craig Casey.
It is only for the second international start for Frawley – who has left Leinster for Connacht – after a run-out at full-back against Wales in the 2024 Six Nations.
Jacob Stockdale and Jimmy O’Brien are selected on the wings with Jamie Osborne moved to full-back after starting the Australia game on the left wing, while Stuart McCloskey and Robbie Henshaw form an experienced centre partnership.
Props Tom O’Toole and Thomas Clarkson – who scored the decisive late try against Australia – start in the front row alongside hooker Ronan Kelleher, who wins his 50th cap.
Beirne is partnered by James Ryan in an experienced second row, while Jack Conan moves from number eight to blind-side flanker to accommodate Jansen’s inclusion, with Nick Timoney selected at open-side.
Farrell’s bench is largely inexperienced at this level. In addition to the uncapped Bohan, Illo and Ward, Ulster pair Tom Stewart and Cormac Izuchukwu are named as pack replacements.
Scrum-half Nathan Doak is set to earn his second cap off the bench with back-up fly-half Harry Byrne poised to make his first Ireland appearance since 2024, while Bundee Aki rounds out the matchday squad.
Ireland beat Japan 41-10 when the sides met in Dublin in November. Japan’s only victory in 11 meetings with Ireland was a memorable 19-12 success at the 2019 World Cup in Shizuoka.
