Mix dashi, sugar, mirin, soy sauce, and salt together in a small bowl.
Heat vegetable oil in a small skillet over medium heat. Add onion; cook and stir until translucent, about 5 minutes. Stir in dashi mixture. Lay pork slices carefully on top of the onions. Drizzle eggs around the slices. Cover skillet and cook until eggs are set, about 2 minutes.
Divide rice between 2 bowls. Top each with half the onions, eggs, and pork slices.