PSG, featuring attacking trio Kylian Mbappe, Neymar and Lionel Messi, will take on J-League sides Kawasaki Frontale, Urawa Reds and Gamba Osaka during their 10-day stay in Japan.
The French champions will then head to Israel to face Cup-winners Nantes in the French Super Cup in Tel Aviv on August 31.
Galthier will lead PSG for the first time since arriving from Nice to take over from Mauricio Pochettino in the summer, and the 55-year-old is eager to get started.
"We have three games against very good opposition," Galthier said at a Tokyo press conference in front of around 100 reporters.
"Japanese football is at a very high level, with players with good technique and speed. I hope these matches will be good preparation for the French Super Cup in Tel Aviv."
PSG have brought a squad of 25 players to Japan, and they touched down at Tokyo's Haneda airport shortly before midday.
The team are scheduled to hold football clinics and open a new academy during their time in Japan.
Their first game will be on Wednesday at Tokyo's National Stadium against reigning J-League champions Kawasaki.
Messi said Japanese football had "taken some big steps forward".
"They're very organised and competitive," said the Argentine star.
"They have become much more physically competitive."
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)