With a number of players on British & Irish Lions duty this summer, it is a chance for some of Wales' younger names to make a name for themselves. But with the likes of Coombs and skipper Bradley Davies in the side, there is also plenty of experience on show.
"We've got fantastic leaders in the squad like Bradley Davies, Blues captain Andries Pretorius and Rob McCusker too," said Coombs.
"It's going to be hard. Japan are a good side, well organised and very well coached. They're targeting this game as one they can win and they're really going to come at us.
"Every game starts up front and we've been basing our training around physicality, getting a good set piece and being dominant."
Coombs and Davies offer some seniority in an exciting looking pack. Scott Andrews, McCusker and Lou Reed join them in providing previous international experience with Andrews and Ryan Bevington completing the front row alongside Phillips.
In the backs, Howells joins up with Liam Williams and Harry Robinson in a dangerous back three with Blues man Owen Williams making his debut at centre. He partners Jonathan Spratt in midfield with the experienced half back pairing of Lloyd Williams and Dan Biggar inside them.
"The team is ready to go to be honest," said Wales attack coach Mark Jones.
"We need to look after the ball and keep it away from Japan. If we do that, I think we'll control the speed of the game and that's our main focus."
While conditions are not likely to be as severe as the ones experienced by the Lions in Hong Kong recently, the heat of Japan will be something new for Wales to contend with.
Jones though, says Wales are well prepared for tomorrow's game.
"The conditioning team have done an excellent job getting this group of players ready so there are no worries there," he added.
"It's warm but the guys have prepared particularly well all week so I don't expect the conditions to be a factor. The only way you gain experience is by playing so this group of players will be a lot better off by the weekend.
"Margins aren't really that important, we're just after a win. Hopefully it will be a successful afternoon for us."
Japan head coach Eddie Jones meanwhile is looking forward to seeing his side test themselves against the Six Nations champions.
"It's not often Japan get to play against Wales," said the former Australia coach.
"They are one of the greatest rugby countries in the world, produce top players and have a great belief in the way they play the game."