The Welsh, who have lost 15 players as well as head coach Warren Gatland to the British and Irish Lions, face two Tests in the Far East.
"It's definitely a huge test for us going out there," Edwards said on the Wales Rugby Union official website. "Japan are an improving nation and we have to deal with the heat and the humidity, plus the fact that we will have approaching 30 players missing."
Experienced players like Ryan Jones and Matthew Rees have been left out of the squad while Aaron Shingler and Ashley Beck became the latest in a line of players to miss out through injury, meaning call-ups for Cardiff Blues flanker Josh Navidi and Scarlets centre Adam Warren.
Scarlets player Shingler has failed to recover from a foot problem, while Ospreys man Beck has picked up a groin complaint.
Edwards added: "But we seem to have a resolute bunch of lads and we've got up to speed over the past couple of weeks in training.
"As a coach you find you work harder with young, inexperienced players in that there's more to teach. Sometimes you need a little bit more time with them. At the moment we're pretty pleased with them. The attitude is fantastic. I'm quite impressed by their improvement."
Wales' first Test is in Osaka on June 8 and the second in Tokyo a week later.
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- Warren Gatland
- Aaron Shingler
- Ashley Beck