Street art in Japan ?

I live in Japan for few weeks now and I want to do some ephemeral street art (doing my stuff, take pictures and clean it up at the end of the day).
What are the law/rules about street art in Japan ?

Thanks

Most likely, you'll get arrested and get grilled for several hours. Don't do it without getting a permit in advance. But a permit is not usually granted to a lay person. So in short answer, forgetaboutit.

I would like to have a little more developped answer please. What about those permits ?

I just want to precise that my street art is not graffiti tagging but small (less that 1m2) chalk art on the ground and paper art. I do not degrade buildings.

I googled "道路にチョークで落書き” (Graffiti in chalk on the road) and found the following link.

http://www.rikagaku.co.jp/s_event/?id=119

As Tokyonet stated, graffiti on the road is prohibited in Japan, but in some festivals and events, it is encouraged. When I was a child (almost half century ago), it was very common for children to write something on the road though.

I hope you can find a good opportunity to show your arts in Japan!