First, you should have a Japan Alien Registration Card valid for at least 1 year, then it is possible for you to apply for a multiple-entry visa valid for 6 months, you need to provide your passport, one passport photo, one filled visa application form, Japan Alien Registration Card and its copy, sometimes, the hotel reservation and two-way flight tickets are also required. If you want a business visa, the multiple-entry visa notification form issued by a Economic and Trade Bureau office is required. The invitation letter is not enough.