The Tokyo area uses 100V AC/50Hz.
Devices that take 110V AC will work fine.
The shape of power outlets is identical those used in the United States (two blades in parallel) except most outlets do not have third hole for a ground pin.
Most small shops, taxicabs and train stations do not accept credit cards.
It is advised to carry some JPY cash.
There is no tipping habit in Japan.
VAT of 5% will be added to every purchase you make.
1USD = 110JPY ; 1EUR = 130JPY (roughly)
Most bank ATMs do not take Cirrus/Plus bank cards for withdrawal.
Exceptions are Citibank ATMs and ATMs at post offices.
Citibank ATMs are located in Terminals 1 and 2 of Narita Airport and at the Roppongi crossing. Open 24 hrs.
List of Citibank branches in Tokyo area.
The Japanese cellphone network is not compatible with GSM.
CDMA is in service, however, if you need a cellphone,
(1) rent it at the airport or (2) buy prepaid-card phones at a convenience store.
Late spring in Japan is warm with average temperatures in the low to mid 20's (Celsius). Light jackets, light sweaters are recommended for the evening.
JNTO (Japan National Tourist Organization)
TCVB (Tokyo Convention and Visitors Bureau)
Most Useful & Most Useless Travel Tips in Japan
Narita Airport (NRT)
Tokyo Subway Network
JR (Japan Rail) East