JR East - Japan Railway Company
The JR East train homepage is a great way to learn about train routes, fares and activities throughout what is known as Eastern Japan. This site: http://www.jreast.co.jp/e/routemaps/index.html shows the routes that the different bullet trains take from the Tokyo area to destinations throughout Eastern Japan.
The following website: http://www.jreast.co.jp/e/destinations/index.html is a great site to use so as to determine your areas of interest, locations you would like to visit as well as the different activities going on depending on the season you travel to Japan.
Right now, it is the summer season and also the season that fireworks festivals are held all throughout Japan. http://www.jreast.co.jp/e/season/summer_hanabi/index.html This site shows the major fireworks (hanabi) festivals that are held throughout Japan.
Also, numerous festivals http://www.jreast.co.jp/e/season/summer/index.html are held throughout all of Japan during the summer months. Be sure to include one of the festivals during your visit.