Two other uncapped players, Owen Evans of Llandovery and Jamie Davies of Carmarthen Quins, start on the bench.
Squad captain Scott Andrews, Dragons academy outside-half Dai Langdon and Cross Keys scrum half / wing James Leadbeater are unavailable for this game with minor injuries but should all be available for Wales' second game of the championship against Canada on Tuesday. Ospreys academy no 8 Rory Pitman goes straight into the starting line-up after joining up with the squad from New Zealand where he has been playing with Air New Zealand Cup side Taranaki
Wales head coach Phil Davies said, "The boys have worked extremely hard since we arrived in Japan at the end of last week. The new caps have all performed well in training and deserve their opportunity on the field tomorrow. We are confident in these players and hopeful this team will bring us a winning start to the tournament. However, we have five games over 16 days and therefore a 26-man effort is undoubtedly required in order to do well for Wales in this campaign. Rory (Pitman) is in great shape, he has trained well and fitted straight back into the group well, there is no doubt his time in New Zealand has helped him.
"Being in Japan is providing a new cultural experience for the players, alongside the rugby experience. We visited the Atomic Bomb Museum in Nagasaki this week, an unbelievable experience for the players and management."
Wales Under 20 v Tonga, Friday 5 June, 11am UK time (7pm local time):
Daniel Newton (Scarlets academy/ Llanelli); Jamie Loxton (Blues academy / Glamorgan Wanderers), Jason Harries (Carmarthen Quins), Ashley Beck (vice-captain, Ospreys academy / Aberavon), Nick Reynolds (Llanelli); Matthew Jarvis (Ospreys academy / Neath), Lloyd Williams (Blues academy / Glamorgan Wanderers); Aaron Coundley (Dragons academy /Ebbw Vale), Rhys Williams (Blues academy / Pontypridd), Simon Gardiner (Scarlets academy / Llanelli), James King (Ospreys academy / Aberavon), Ashley Sweet (Dragons academy / Cross Keys), Justin Tipuric (capt, Ospreys academy / Aberavon), Rhys Jenkins (Dragons academy / Ebbw Vale), Rory Pitman (Ospreys academy / Bridgend / Taranaki)
Replacements: Owen Evans (Llandovery), Craig Attwell (Dragons academy/ Newbridge), Josh Navidi (Blues academy / Glamorgan Wanderers), James Thomas (Dragons academy / Ebbw Vale), Rhys Downes (Blues academy / Pontypridd), Jamie Davies (Carmarthen Quins), Scott Williams (Scarlets academy / Llanelli), Dan Partridge (Cardiff)
Wales Pool D fixtures (all at Best Amenity Stadium, Saga):
Wales v Tonga, Friday 5 June
Wales v Canada, Tuesday 9 June
Wales v Australia, Saturday 13 June