Four times Wales-capped full back Tom Prydie will make his Wales Under 20 debut, while Harry Robinson, who has been called up by Wales caretaker head coach Rob Howley for his summer training squad, will also start tomorrow evening on the request of the Wales management in order to get some valuable extra game time.
Jack Dixon (Dragons), captain Cory Hill, and Luke Hamilton (both Blues) return to the Wales Under 20 starting line-up after staying with their Regions for the majority of the Under 20 Six Nations.
Wilson said: "This match against Japan is a very important part of our Junior World Championship preparation. It is the first real chance to see some of the players in action who have had little or no game time for us this season, and after a very intense and competitive series of training sessions, that will be exciting to see.
"The game will give us a chance to see almost all of our squad, along with some of our reserve players and give players a chance to stake a claim for places in the starting line-up against Fiji, our opening JWC Pool game. We are working with the Ospreys to manage their players who obviously have a the RaboDirect Pro12 final to prepare for but everyone should have some game time.
"Japan narrowly lost to a Welsh Academicals side in a very high scoring game on the weekend and they were very competitive against Samoa in the Junior World Trophy final last season so they will be no walk-over but our main focus is on fine-tuning our own game."
Wales Under 20 v Japan
Tuesday 15 May 7.15pm, St Helens, Swansea (Entry £5 for adults, Under 16s go free)
Tom Prydie (Ospreys / London Wasps); Harry Robinson (Blues), Jack Dixon (Dragons), Owen Williams (Scarlets), Luke Morgan (Ospreys); Sam Davies (Ospreys), Jonathan Evans (Dragons); Rob Evans (Scarlets), Kirby Myhill (Scarlets), Samson Lee (Scarlets), Cory Hill (capt, Blues), Matthew Screech (Blues), Luke Hamilton (Blues), Daniel Thomas (Scarlets), Dan Baker (Ospreys)
Replacements: Darran Harris (Blues), Jamie Sollis (Dragons), Gareth Thomas (Carmarthen Quins), WillGriff John (Blues), Rhodri Hughes (Ospreys), Jack Jones (Ospreys), Reuben Tucker (Ospreys), Ieuan Jones (Dragons), Ellis Jenkins (Blues), Rhodri Williams (Scarlets), Matthew Morgan (Ospreys), Thomas Pascoe (Blues), Cory Allen (Blues), Iolo Evans (Scarlets), Ross Jones (Ospreys)