Beach camp
The beaches are lovely, but there's often quite a lot of rubbish on them, mostly washed up out of the sea I presume, although there is definitely a fly tipping/litter problem in some places too by the roadsides, etc. Japan's lack of public litter bins doesn't seem to make it any worse than the UK for litter, but it's a bit more frustrating for touring cyclists! Luckily most of the konbini (convenience store) have litter/recycling areas.
Plastic packaging is excessive and all apart from plastic bottles seems to go into the 'burnable' bin. Then they recycle cans, but maybe not other metals with them. Could be better on the main Japanese islands though I suppose...