McGrath gets Ireland start
Coach Joe Schmidt handed scrumhalf Luke McGrath his first Test start as part of a revamped backline in which wing Keith Earls is the only survivor.
Simon Zebo, Andrew Conway, Rory Scannell and Paddy Jackson also come into the backs, while flank Dan Leavy for Josh van der Flier is the only change in the forwards.
Ireland captain Rhys Ruddock is joined in the back row by Dan Leavy and Jack Conan.
Quinn Roux and Devin Toner are paired in the second row with Cian Healy, Niall Scannell and John Ryan filling the front row positions.
McGrath makes his first start for Ireland at scrumhalf and his halfback partner is Paddy Jackson.
Rory Scannell starts at inside centre alongside Garry Ringrose in midfield and there is an all Munster back three combination with Simon Zebo at fullback and Keith Earls and Andrew Conway named on the wings.
There are two uncapped players among the replacements – Kieran Treadwell and Rory O'Loughlin alongside James Tracy, Dave Kilcoyne, Finlay Bealham, Jack O'Donoghue, Kieran Marmion and Tiernan O'Halloran.
Saturday's game in Shizuoka, the first of two Tests, comes after Ireland ran in nine tries in their 55-19 victory over the United States last week.
Ireland have never lost to Japan, the 2019 World Cup hosts, but their last Test series against them was 12 years ago in 2005.
Ireland: 15 Simon Zebo, 14 Andrew Conway, 13 Garry Ringrose, 12 Rory Scannell, 11 Keith Earls, 10 Paddy Jackson, 9 Luke McGrath, 8 Jack Conan, 7 Dan Leavy, 6 Rhys Ruddock (captain), 5 Devin Toner, 4 Quinn Roux, 3 John Ryan, 2 Niall Scannell, 1 Cian Healy.
Replacements: 16 James Tracy, 17 Dave Kilcoyne, 18 Finlay Bealham, 19 Kieran Treadwell, 20 Jack O'Donoghue, 21 Kieran Marmion, 22 Rory O'Loughlin, 23 Tiernan O'Halloran.
Date: Saturday, June 187
Venue: Ecopa Stadium, Shizuoka, Japan
Kick-off: 14.00 (06.00 Irish time; 05.00 GMT)
Referee: Mathieu Raynal (France)
Assistant referees: JP Doyle (England), Alex Ruiz (France)
TMO: Glenn Newman (New Zealand)
