The Japanese government decided to put an additional charge cost to the people who choose to get a plastic bag at the store, effective from July 1st, 2020.
Except for plastic bags which are containing more than 25% of biomass materials, this rule will apply to each shopping. So you are no longer able to get a plastic bag for free in Japan.
Minister of the Environment in Japan announced at G20 Ministrial Energy & Environment Leaders Meeting that the government mandates to charge fee to get a plastic bags which is using at the store. It's the first time that announce effective date. This is the effort to reduce parley waste in the oceans which is main topic at that conference. By this action, the government encourages to consumer's concious about the disposable plastics.
Quoted from: Nikkei (Japanese article) / Translated by Takuro Fukuda
Some stores were enforcing this rule before the effective date. But from July 1st, 2020, all stores, including a convenience store and the drug store starting to follow this rule. Typically, you can get a plastic bag for 2 JPY ~ 10 JPY per plastic bag.
Each time, you have to ask it at the checkout when you need it.
The cashier will ask whether you need to get a plastic bag or not by saying "Rejibukuro ha hitsuyoudesuka" or "Fukuro ha irimasuka"? Then, you can answer by saying the following words.
If you need one
If you DON'T need one
When you are ready to visit/come back to Japan, you should make sure that you will bring your bag to the store to avoid extra charges at each store. It will save tons of money if you are likely to do much shopping. Also, it's a good idea that you remember the above words.