Delray Beach, Fla.--Office Depot Inc., the world's largest online seller of office supplies, has launched a Japan site. It will allow business customers to purchase everything from fax machines to staples online. Office Depot is the latest among a blitz of b-to-b companies that have recently started Japan ventures, including VerticalNet Inc. and Oracle Corp. Though the country has been mired in a decade-long recession, U.S. marketers are increasingly placing stakes there. Japan's gross national product is second only to the U.S.