France will be another level says Japan coach
But Joseph warned his team that France would represent a different level of challenge when he takes the 2019 World Cup hosts to the new U Arena outside Paris next weekend.
"I'm really proud of the team," Joseph said after the easy win in Toulouse.
"We played a very physical team today and for much of the match, we matched the physicality.
"Our attack and defence were very clinical, we didn't concede any tries.
"Playing France in Paris is a very different challenge for us, we are going to come up with a Tier One team at home.
"But now we can go on to that game with an element of confidence and we can go to play our own game which I think is going to be exciting for the boys,"
It was a Japanese player of Tongan origin, Lomano Lemeki, who opened the scoring after 14 minutes in front of 4 500 spectators at the Ernest-Wallon stadium.
Amanaki Mafi scored back-to-back tries before Japan's captain Michael Leitch increased the margin further and Tonga never recovered.
Tonga coach Toutai Kefu bemoaned a lack of preparation time for his side.
"It is a performance I expected from Japan, they are a really well prepared team, they have a lot of resources at their disposal," he said.
"It is definitely an issue, we don't have our players much of the time, they play in France, in New Zealand, in England.
"It's hard but we just deal with it,"