score:5
By law, you are not supposed to remove consumables from the bag they're placed in until you depart Japan. This seems to be very rarely or never enforced, though.
Purchased items must be kept in the specified bag until leaving the country.
The departure customs counter at which you drop off the form in your passport is often not manned (and will have a drop box for the form in your passport), and when it has been manned, people have been told that it's OK to have the items to be exported in your checked luggage.