Heat sesame oil in a skillet over medium heat; cook and stir eggplant and orange bell pepper until softened, 8 to 10 minutes.
Whisk miso, soy sauce, ginger, vinegar, water, and garlic together in a bowl until sauce is evenly combined; add to eggplant mixture. Cook and stir eggplant mixture until sauce is thickened and glossy, 3 to 4 minutes. Top mixture with sesame seeds.
