ADSL
There are two options for getting internet in Japan, and ADSL is one of them. ADSL has the advantage over fiber optic of being available immediately in most places in Japan. If you choose to get ADSL, you will have to sign up for a phone line through NTT, in addition to your contract with your provider (Yahoo BB, Plala, etc.). This causes the overall price of the plan to be higher than that of fiber optic in most cases. ADSL is also generally slower than fiber. In most cases, if there is fiber optic available it will be the better option.
Fiber Optic
Fiber Optic, called Hikari Fiber in Japanese, is the faster and cheaper of the two options. The only downside is that it might not be available in some areas, and if your apartment is an older building you may need the permission of your landlord to have construction work done to make your building fiber optic-ready.
Internet Service Providers
Yahoo BB
Yahoo BB is one of the most popular internet providers in Japan. You can sign up online, but the site is in Japanese only:
http://bbpromo.yahoo.co.jp.
NTT Communications
NTT Communications is another one of the big internet providers. Being that they’re part of the NTT group (the telephone company), it’s sometimes easier working with them.
http://506506.ntt.com/english/index.html
BB Apply
BB Apply is an agent for Yahoo BB and NTT which offers English support in setting up internet service.
http://www.bbapply.com/jet/index.html
eo Hikari
An affordable fiber optic provider with good service.
http://eonet.jp/
Internet Phone
In addition, internet phone is included with many internet plans. All you will need to do is make sure that it is activated (activation is usually free), and then plug in a phone to the appropriate slot in your modem. The costs will vary from company to company, but YahooBB generally has the best prices for overseas calls, especially those to the USA.