Combine pork, 1 tablespoon shoyu, 1 teaspoon salt, 1/2 teaspoon sugar, and 1 slice crushed ginger in a bowl. Let marinate for 15 minutes.
Heat oil in a large skillet over medium heat. Add pork with marinade; cook and stir until pork is browned, about 5 minutes. Stir rice roll strips into the skillet; cook until edges start to brown, 3 to 5 minutes.
Stir bean sprouts, celery, string beans, green onions, 2 tablespoons shoyu, 1 slice crushed ginger, 1 teaspoon salt, 1 teaspoon sugar, 1/4 teaspoon monosodium glutamate, and pepper into the skillet. Cook and stir until string beans are tender, about 10 minutes. Garnish with sesame seeds.