Watch out for the contract period "Shibari".
In Japan, there are three major Internet carriers, NTT, KDDI au and SoftBank. They usually offer discounts if you agree to use their service for a certain period, for example, 2 years for the initial contract period etc,. This offer is, of course, a good deal but what you should be aware of is that they will charge you a penalty fee if you cancel the contract before the end of the contract period. Also, you should know that the contract is automatically renewed and extended for another period unless you cancel within the month when the contract expires. This usually happens before you know it and tend to miss the timing to cancel without paying a penalty fee. This contract style must be as the same as it in other countries.
For example, if you have a 2-year contract starting in August, the contract ends on the August 2 years later. If you don't want to renew the contract, you need to go through a cancellation procedure within the August. Otherwise, the contract period is automatically extended for another 2 years. If you miss the timing and cancel the contract in September or later, you are considered to break the contract and will be charged a penalty fee. If you want to cancel without paying the annoying fee, you will have to wait for August after the next year. We call this term commitment “Shibari しばり” in Japanese.
Users can check the expiry by checking bills or his/her user account, but nobody pays much attention as long as an occasion comes up such as relocation.
A little good News. They have reviewed their services
Since too many customers are unhappy with the automatic extension system, the major carriers (NTT and Softbank) have extended the allowable cancellation period from one month to two months. For example, cancellation can be made within July and August) if the contract ends in August.
High-Speed Network Carriers in Japan
*NTT West and NTT East provide different fiber-optic services each other, in operation covering in different areas. If you move from eastern Japan to western Japan, chances are that you will have to cancel the contract with NTT East, then have a new contract with NTT West. See their coverage - http://www.ntt.co.jp/product/category/area.html
Nuro by So-net
Mobile/Wireless Network Carriers in Japan
Related Info : Paid Wi-Fi Services
These services are usually provided without minimum contract period. The fee is paid on a monthly basis by credit card.
Yahoo BB Wireless LAN Spot Services
http://wireless.yahoo.co.jp/ (Japanese Website)
This service allows users to have Internet access at hot spots, including Japan MacDonald.
OCN Wireless LAN Spot Services
http://service.ocn.ne.jp/mobile/hotspot/ (Japanese Website)