Place chicken thigh, sake, and salt and pepper in a microwave-safe container. Cover loosely with plastic wrap and microwave at 600W for 5 minutes. Let it steam for 4 minutes with the wrap on.

Mince the green onion.

Boil water in a pot, add 1 tsp salt (not included in ingredients), and cook the capellini according to package instructions. Rinse with cold water and drain.

Cut the chicken into bite-sized pieces. In a bowl, mix the chicken's steaming liquid with the sauce ingredients.