Every electric shop like Yodobashi, and some cell career shop. Tend to be sold in weekend/holidays.

Technically it should be sold for everyone in $190 (22,000JPY), but some shops don't want to sell without contract. Govt make a regulation that limits discount for new contract to 22,000 JPY and careers must sell phones without contract. So shops should set non-contract price to 22,000, to sell for 0JPY for new sign up.

IOSYS has really cheap secondhand simfree iphones

Yes it's also easy way to get cheap new open box one.

The used ones there are usually good as new, Japanese have dislike for used things, so they don't really put out the ones that are really damaged or have lots of scratches.