I always thought it was to the gods, spirits, kami, whatever "it" or "they" were that allowed you to eat. Though it could be either, or both at once; when members of Native American tribes would make a kill on the hunt, they would pay their respects to the spirit of the animal they just killed. Even if it was the spirit of a fish they had just speared, giving its life so they could eat another day.

I kind of admire the Japanese for their capacity to live humbly and gratefully without need for a big-sky-daddy myth. The world of the traditional Japanese is full of hidden wonders; indeed, it really belongs to them, and we just live in it.