It seems very common in Japan to see people playing music in the street, everywhere. I saw lot of musicians and singers down the Kamogawa river in Kyoto at night. If the weather is good I suggest everyone to pass one evening by the shore and listen to random musicians. But it is also easly to find people playing in Osaka and also in smaller city like Hirakatashi, I met some guitar players down the station there really good.
So, it seems kind a normal behavior for japanese young musicians to stop in the street and play, with all the amplications and often with friends that help them. In other countries such Italy, playing in the street is related to people that beg for money. In England instead there are just few spots in the street or in the tube where is legally possible to play and only few people that registered themselve at the city hall can do it.
Japan looks more freedom for everyone that want express its art, at least musicians. Some day ago I passed by Osaka station and, over the bridge, there was a full band playing live in front of 30 people more or less. It was quite nice, they where playing J-pop while trains where running behind them. The bad was called KAEDE, formed by drums, bass, guitar and young girl as singer. They where selling and promoting theire new cd and the future live performance in clubs. The price for the cd was affordable, 1000 yen. So, I suggest to take a look on theire website for more informations: http://www.edeak.net/. If you also want to vote for them in a contest you can do it here!
I also discovered a really nice Japanese band, they are already really famous! The band is called Tokyo Jihen and the beautiful singer is Shiina Ringo.
Here are some links if you wanna have a look:
Official web site (under construction)