Prepare ingredients: Chop vegetables finely and break up rice clumps.
Heat pan: In a large skillet or wok, heat vegetable oil over high heat until shimmering.
Cook vegetables: Add onion and carrot, stir-frying for 2-3 minutes until softened.
Add protein: If using ham, chicken, or tofu, stir-fry for 1 minute.
Scramble eggs: Push ingredients to one side, pour in eggs, and scramble until just set (30 seconds). Break into small pieces. Skip for egg-free version.
Stir-fry rice: Add rice, spread evenly, and let sit for 30 seconds to crisp. Stir-fry for 2-3 minutes.
Season: Add soy sauce, mirin, salt, pepper, and MSG (if using). Stir-fry for 1 minute.
Finish: Toss in green onions, stir for 30 seconds, and serve hot.