International prepaid android smartphone?

so im stationed in japan for the next few years, and all i want is a prepaid android phone with (hopefully) unlimited data. not concerned on minutes. The local phone company here, Softbank, is too shady for me. they wont let u pay your own bill and take the money as they want. i had verizon in the states and had to suspend it intill i return. but back to the subject, i just need an android with access to japan's networks. i use apps to communicate. and its getting annoying having to hunt down a wifi spot to use my old android. i just want network access so i can be mobile