Doesn't the fact that you had to research extensively before coming here to be able to get an MVNP SIM for data prove the point at how backwards Japan is in regards to Payn'Go?
I'd like to know which MVNPs in Japan are offering both voice and data without a contract—I only know of the BIC SIM and perhaps a B-mobile SIM and both require proof of residence, but I could be wrong as things are changing here. Yes, I stand corrected, there are now some MVNP data-only providers who don't need a contract, but messing with SIL and SIP phone settings is beyond what most people want to do, although LINE makes it much easier. Japan is a sophisticated mobile market in many ways but the inability to buy a Payn'Go SIM from a corner shop, put it in an unlocked phone, and start making phone calls and using data instantly puts Japan behind many developing countries where full voice and data SIMs can be bought almost anywhere. I have a suspicion that it is due to Japan's National Police Agency wanting to keep a tight lid on knowing who has what phone number but have never heard that said in public.
For those visiting Japan and needing a data SIM, here is an extensive list of who offers what, but you need to read Japanese!
I'll state the obvious and point out the obscene levels of "misuse" of phones enabled with a camera. It's a bit of a pain in the ass to get a data-only sim even in the US if you're from outside the US. Why Japan seems any different is probably a matter of perspective.