A guard is at your door and wants some of your grains. This is the tax you pay for living in this town. Back in the day, grains were used like currency, so it makes sense that there was a grain tax in the olden days.
You have to pay this tax, because if you don't the guard will cut you down with his special German saber, a zeiber (ぜい). "Don't you hear vat I zei? Pay ze tax or I vill zlei you!" he shouts.