Tbf there's a konbini with trash cans every few hundred meters. Only issue being if you don't buy something it's not considered ok to use them afaik, but can just buy sth to eat immediately and throw away the packaging there or just something smaller than your trash and bring it with you after.

Or honestly ignore it because realistically as a tourist all your trash came from the previous konbini anyway and it would just even out. Just don't go there to dump whatever.