Whisk soy sauce, garlic, ginger, monosodium glutamate, salt, black pepper, and sesame oil together in a bowl until salt dissolved; pour into a large resealable plastic bag. Add chicken thighs, coat with marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator for 1 hour.

Remove thighs from marinade and shake off excess. Pour marinade into a programmable electric rice cooker.

Whisk 2 tablespoons water and cornstarch together in a small bowl until smooth; whisk into marinade. Add thighs and just enough water to barely cover; stir.

Seal rice cooker and select regular rice setting according to the manufacturer's instructions. Cook until steam comes out of cooker's top, about 20 minutes. Set cooker's timer for 10 minutes; cook. Unlock cooker; stir. Set cooker's timer for 10 minutes; cook. Switch cooker to keep warm setting; rest chicken in cooker for 20 minutes.