Citizens of some countries can enter Japan for short-term stays without a visa, for purposes of sightseeing Tokyo and even for business trips.

All visitors coming for a Tokyo vacation must have a valid passport, onward or return tickets, and sufficient money to cover the expenses of their stay.

There are many countries that have "Visa Exemption Arrangements" with Japan and do not need an entry permit:
For a period of 6 months or less -
Austria, Germany, Ireland, Liechtenstein, Mexico, Switzerland and the United Kingdom.

For a period of 3 months or less -
Argentina, Bahamas, Belgium, Canada, Chile, Costa Rica, Croatia, Cyprus, Denmark, Dominican Rep., El Salvador, Finland, France, Greece, Guatemala, Honduras, Iceland, Israel, Italy, Lesotho, Luxembourg, Macedonia, Malta, Mauritius, Netherlands, Norway, Portugal, San Marino, Singapore, Slovenia, Spain, Suriname, Sweden, Tunisia, Turkey and Uruguay.

For a period of 90 days or less -
Andorra, Australia, Barbados, Bulgaria, Czech Rep., Estonia, Hong Kong (BNO, SAR passport), Hungary, Rep. of Korea, Latvia, Lithuania, Macau (SAR passport), Monaco, New Zealand, Poland, Slovak Rep., Taiwan and the U.S.A.

For a period of up to 14 days -
Brunei

If you're planning on coming to Tokyo soon, here's the basic Tokyo information regarding Japan visa Requirements and Getting ready for Tokyo - Planning to Work in Tokyo? If you want to enter Japan for activities other than sightseeing, such as working for a Japanese company or teaching English in Japan, you need a Japan work visa.