Good place to sleep in my tent?

I was thinking about going to Japan with the idea of sleeping in my own tent.
That might be crazy in August, but I'm already determined.

Is there some place where I would have no problem setting my tent?

It should be in Kansai (would land at Osaka) or Kyushu (would land at Fukuoka).

Those two options are equally good for me.

I'm just asking in case you say "oh yes! there is this place that is perfect for tents!"

If there is none, it's ok, I'll keep searching :)

Thank you in advance ^^

Is there some place where I would have no problem setting my tent?

Designated camp grounds. Here are lists of camp grounds:
http://www.mapple.net/camp/
http://www.campjo.com/
http://www.jnto.go.jp/eng/location/rtg/pdf/pg-804.pdf

Everywhere else you would have to inquire with the land owner or the local authorities whether setting up your tent is permitted.

Excellent! Looks like Japanese websites are much more complete, the ones I found in English were not so good.

I found a great campsite using your first website, mapple, thank you so much!! :)