Preheat oven to 350°F. Place a non-stick 9 x 5-inch loaf pan in the sink.
In a small bowl, stir together 1 tablespoon of the yellow mustard with 1/4 cup ketchup.
In a large mixing bowl, break up the wagyu and the ground pork using your hands and mixing as you go.
Add the chopped onion, Kosher salt, black pepper, garlic powder, remaining yellow mustard, remaining ketchup, eggs, cubed bread, and milk.
Loosely pack the meat mixture into the prepared loaf pan, pressing down only once you've filled the pan.