Undertale-inspired, fantasy world, Papyrus, Sans, Toriel, Asgore, underground, ruins, ancient structures, mystical aura, glowing mushrooms, twinkling starlight, soft focus, warm colors, dreamy atmosphere, character interaction, friendly poses, gentle expressions, casual clothing, jeans, hoodies, sneakers, relaxed posture, leaning against walls, sitting on rocks, peaceful music, gentle breeze.