Wales have named four uncapped players to start in Saturday's first Test against Japan in Osaka.
Lock Bradley Davies, who has 38 of those caps, will captain the side for the first time.
Fly-half Dan Biggar is the only survivor from the team that beat England to win the Six Nations title.
Davies, Biggar and scrum-half Lloyd Williams are the only players to have reached double figures of appearances, leaving Wales to field their least experienced side of the professional era.
"It's a fantastic opportunity for the new caps and they know the importance of representing our nation," said coach Robin McBryde, at the helm in Warren Gatland's absence with the British and Irish Lions.
The Lions have also deprived Wales of 15 leading players, while Ryan Jones, James Hook and Paul James have been rested as Wales look to blood new talent.
Fly-half Rhys Priestland, hooker Ken Owens, flanker Aaron Shingler, prop Craig Mitchell and centres Scott Williams and Ashley Beck are all out injured.
Wing Howells enters the international stage having played just seven games of senior rugby - five with Neath in the Principality Premiership and two for Ospreys in the LV= Cup.
The 18-year-old, the youngest player named in Wales' squad, showed his promise with a classy try for Neath from the halfway line in the Swalec Cup final loss to Pontypridd in May.
Fellow debutant Williams, 21, will form a centre partnership with 27-year-old Jonathan Spratt, whose two previous Wales caps were on the 2009 tour to North America.
Once capped Harry Robinson is the other wing, with Liam Williams at full-back.
With Exeter prop Mitchell ruled out after arriving in Japan, new cap hooker Phillips (26) is between Six Nations squad members Ryan Bevington and Scott Andrews in the front row.
Captain Davies is alongside Blues teammate Lou Reed in the second row, while Dragons player Andrew Coombs, who played at lock for Wales in the Six Nations and is the oldest team member at 28, is at blindside flanker.
King will be in an unfamiliar role of open-side flanker for his first taste of Test rugby, with Rob McCusker completing the back row in his first start for Wales at number eight.
"The squad have really worked hard over the last couple of weeks and they are ready to get out and play," said coach McBryde.
Another four players could make their debuts, with hooker Scott Baldwin, back-rower Dan Baker, flanker Andries Pretorius and Rhys Patchell named on the bench.
Japan have made seven personnel changes and three positional switches after losing to Fiji for Saturday's game.
Former Australian rugby league star Craig Wing is recalled at centre while Super 15 pair Fumi Tanaka at scrum half and Shota Horie at hooker also start.
Japan have recruited former England lock Steve Borthwick to help in their preparations.
Wales: Liam Williams (Scarlets); Harry Robinson (Blues), Owen Williams (Blues), Jonathan Spratt (Ospreys), Dafydd Howells (Ospreys); Dan Bigger (Ospreys), Lloyd Williams (Blues); Ryan Bevington (Ospreys), Emyr Phillips (Scarlets), Scott Andrews (Blues), Bradley Davies (capt, Blues), Lou Reed (Blues), Andrew Coombs (Dragons), James King (Ospreys), Rob McCusker (Scarlets).
Replacements: Scott Baldwin (Ospreys), Rhys Gill (Saracens), Rhodri Jones (Scarlets), Andries Pretorius (Blues), Dan Baker (Ospreys), Tavis Knoyle (Scarlets), Rhys Patchell (Blues), Tom Prydie (Dragons)
Japan: Ayumu Goromaru, Yoshikazu Fujita, Male Sau, Craig Wing, Kenki Fukuoka, Harumichi Tatekawa, Fumiaki Tanaka; Masataka Mikami, Shota Horie, Hiroshi Yamashita, Hitoshi Ono, Shoji Ito, Hendrik Tui, Michael Broadhurst, Takashi Kikutani (capt).
Replacements: Takeshi Itu, Yusuke Nagae, Kensuke Hatakeyama, Toshizumi Kitagawa, Ryuta Yasui, Atsushi Hiwasa, Yu Tamura, Hirotoki Onozawa.