Ministry of Economy, Trade and Industry is working on a registration mandating plastic bags used at stores in Japan can no longer given away for free. The Ministry is working to have this new registration go in effect on April 1 next year. If this registration go through then in Japan all stores will be required to charge fees if you need plastic bags when you shop at stores.
The news article I read specifically says plastic bags, so I am assuming paper bags can be continued to be provided for free under this new registration.
P.S.
I have tons of those disposable Oshibori (wet towel) packs form all those Konbini visits. And you think on Green Car on JR trains those disposable Oshibori pack come as a part of added service for Green Car fare paying passengers

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