Lightly season shrimp with salt and pepper. Set aside.
Heat oil and 2 tbsp butter in a skillet over medium-high. Cook shrimp for 3 minutes, flipping once. Remove.
Add mirin, scraping up brown bits. Let it reduce for 30 seconds.
Add onions, carrots, and 1 tbsp butter. Cook 3–4 minutes until soft.
Push veggies aside. Add butter, pour in eggs, scramble, then mix with veggies.
Stir in rice, garlic powder, sesame oil, and remaining butter. Heat through.
Add soy sauce, oyster sauce, shrimp, peas, and corn. Stir and cook 2–3 minutes.
Season to taste. Top with green onions and serve hot.