Whether a visa is needed when visiting Japan depends on the foreigner's:
Singapore Citizens (holders of Singapore passport) who intend to stay in Japan as tourists for a period of up to 3 months do not need a visa.
For further information on visas, please visit the following websites:
Embassy of Japan
Ministry of Foreign Affairs
Notes: In the case of the waiver of visa requirements of up to three months or 90 days, foreigners are granted upon landing a temporary visitor status for a period of 90 days (15 days for Brunei). Nationals of countries and regions that have taken measures concerning the waiver of visa requirements with Japan for stays of up to six months in principle are granted permission to stay in Japan for 90 days at the time of landing. Nationals of these countries and regions who wish to stay in Japan for more than 90 days must apply at their nearest immigration authority in Japan for an extension of their period of stay.