List of places and times to see fireflies

So with summer in full swing, this may be a touch late but when in Japan in the hotter months i quite like going out and seeing fireflies. Just like the cherry blossom front, there is somewhat of a similar thing for fireflies.
Unfortunately, the most amazing place i saw them was about 40mins drive north of Hamamatsu in Shizuoka. Sorry, i have no idea how to get back there. We were in a field with a river about 50m away and as the sun went down below the mountains, a few little green lights started to dance above the grass near the river. Soon those few lights turned to hundreds and probably thousands and they moved across the field until we were surrounded by little green lights. It was pretty spectacular.
I thought this might be a good spot to put your favourite locations and best times to see fireflies.
The Fussa firefly festival is quite famous (http://www.fussakanko.jp/pa0206.html) but that has passed on the 16th but i'm sure the fireflies are still there. Any others?

In Kanto area, the firefly season is about to end. If you go to the north like Iwate, Aomori, etc they say you will have a chance to encounter them until mid or late July.

http://tabidoki.jrnets.co.jp/e07/event/133841.html

daily update report
http://weathernews.jp/ip/info/hotaru/
Yellow : now peak (Hotaru life about one week)
Orange : Hotaru front (from south to north)

List of Kanto (in Tokyo and near area most overed)
http://www.rurubu.com/season/summer/hotaru/list.aspx?ac=2
http://www.rurubu.com/season/summer/hotaru/list.aspx?ac=2&p=2
http://www.rurubu.com/season/summer/hotaru/list.aspx?ac=2&p=3

Rurubu...of course. Should've been my first stop to check for something touristy!
700Y isn't expensive but the cheek to charge! Especially considering there are hundreds of free places to go.