Update 18/11/17: Must show proof of staying in Shizuoka with hotel confirmation, etc.
Shizuoka City is offering free WiFi router rental, NINJA WiFi, to foreign visitors. With NINJA WiFi, you can stay connected anytime and anywhere in Japan!
I have found this free rental while searching the tourist information. You must pick it up from Shizuoka city which is located 1 hour west of Tokyo or 1.5 hour east of Kyoto by bullet train. If you are using JR pass from Tokyo to Kyoto, you can drop by at Shizuoka station to pick up the free rental. The information center is located in the JR station and they are open anyday from 9:00 to 17:45. The maximum days you can rent is 15 days and unlimited MB of download.
The official site tells you to return at an airport, but according to this website, it looks like you can send it back for return from any convenience store in Japan.
https://shizuokatourism.com/2015/12/01/fee-wifi-rental-for-f…
I also found a similar service in Tokyo. However, this is only for 3 days and need to go back there to return. You can rent it from Skytree, Azumabashi (Near Asakusa) or Ryogoku (Sumo Stadium).
http://visit-sumida.jp/inbound/
http://visit-sumida.jp/wp-content/uploads/2015/06/wifi_mobil…
http://visit-sumida.jp/wp-content/uploads/2015/06/wifi.pdf
New information:
There is a similar service available in Kochi prefecture.
http://www.pref.kochi.lg.jp/soshiki/020201/files/20160705001…
It is available from 11/July/2016 to 31/Mar/2017 and you can rent it for 3 days according to their website.
Niigata Prefecture:
Free rental is also available from Niigata prefecture. Echigo yuzawa in Nigata prefecture is a famous hot spring and ski resort and about 70 min from Tokyo. The ski resort is very near to the station. Local people go there for a day trip from Tokyo.
This is available from 16/Jan/2017 to 31/Mar/2017.
1. Foreign visitor visiting Niigata prefecture
2. 1 device per group. Up to four days.
3. You must upload it Facebook.
Pick up from one of these locations:
Niigata Airport
JR Niigata station tourist information centre
JR Echigo Yuzawa station tourist information centre
God I wish I had this when I went earlier this year…