Mix white miso, sake, soy sauce, brown sugar, and sesame oil together in an ovensafe glass or ceramic baking dish. Stir in chicken strips. Cover with plastic wrap and let marinate in the refrigerator, at least 30 minutes.
Preheat oven to 375 degrees F (190 degrees C).
Bake in the preheated oven until marinade has thickened and an instant-read thermometer inserted into the chicken reads at least 165 degrees F (74 degrees C), 30 to 35 minutes.