[Sangetsu]

It's available, but it's not free. You'll find wifi at McDonald's, Starbucks, and the like, but you'll need to pay for it. I am writing this reply on my iPad using Docomo's pocket wifi, which runs about 5000 yen per month for unlimited service. You need to sign up for a 2 year contract to get it, and you need a alien registration card to get a contract.