Loads of stuff to do, try The Cave in Shinjuku, also Yellow, also try going out of Tokyo, there are some good clubs in Fukoka as well, and a few tiny ones in Kumamoto.
Otherwise other stuff to do such as the Spring Bath Volcanoes at Aso, The museums at Nagasaki and Hiroshima are worth visiting as well,
If you feel like experiencing the countryside, try vising the Amaxa Islands (off the coast of Kyushu) try visitng some Taiko groups (Japanese Drumming) as well.
If you feel like buying some electrical goods go to Akihabara (Tokyo) otherwise known as electric town.
