Duty free
Quicky: I’m not sure if I’ve mentioned it before, but if so, it cannot hurt to reiterate the following.
When you shop for non-perishable goods (that is, non-food, for example), you are eligible for a tax refund or deduction on those items. That is, only if you are a tourist not living in Japan.
In some stores in the more touristic places, signs (or other methods) in the stores will indicate this as well.
Elmira (my host in Nagoya) mentioned that it is also possible to get a refund at some designated location at the airport. I might check that out, if there is enough time before departure.