Cut the nori sheet into two equal pieces.

Place the chicken thigh skin-side down and make four vertical cuts. Flatten the chicken with your hand using plastic wrap, pierce the skin with a fork, and season with salt and pepper.

Place the nori and string cheese on the chicken, then roll it tightly from one end. Secure with toothpicks.

In a microwave-safe dish, mix the sake, mirin, sugar, and soy sauce. Add the chicken roll and coat it with the mixture. Cover loosely with plastic wrap and microwave at 600W for 5 minutes.

Turn the chicken roll over, coat it with the sauce again, cover loosely, and microwave for another 4 minutes. Let it rest with the wrap on for 5 minutes to cool slightly.