The rate of Japanese consumption tax is currently 8%. All goods and services are taxed at 8%, except for tax-free ones which are a transfer of land, securities and so on. However, the consumption tax rate will increase by 2% on October 1 and reduced tax rate system will also be introduced at once. The system is that the consumption tax rate of foods and newspapers will decrease by 2% on October 1. The items that are necessary for our daily life will not be taxed at 10% but foods served in restaurants will be taxed at 10%, because the price of foods in restaurants includes services by staff.
For example when you buy fruits in a supermarket after October 1, the consumption tax rate is 8%. When you eat ramen in a restaurant after October 1, the consumption tax rate is 10%. These examples are easy.
For another example when you buy a burger in McDonald's and take out a burger after October 1, the consumption tax rate is 8%. When you buy a burger in McDonald's and eat it their stores and premises after October 1, the consumption tax rate is 10% because it includes the services by their staff. These examples are a little difficult.
That is why I recommend choosing take-out rather than dine-in in McDonald's when you travel in Japan after October 1.