- In a small bowl, stir together soy sauce, mirin, sake (or water), and sugar. Set aside. 
- Heat oil in a non-stick skillet over medium heat. 
- Add chicken thighs and cook until golden brown on both sides, about 5–6 minutes per side. 
- Pour in the sauce and let it simmer until thick and glossy, turning chicken occasionally to coat well. 
- Slice chicken, spoon sauce over the top, and garnish with green onions and sesame seeds if desired. 
- Serve with rice or steamed vegetables.