Your pants and undergarments had only been taken halfway off, limiting the mobility of your legs. Mettaton knew what he was doing. He traced a line of warm pink goo down your torso, stopping right above your sensitive area. You rattled, feeling the heat the heart gave off. Then he decided, no, not yet, and avoided your genitals and pressed the heart to the inside of your thigh.
"Ah, shit," you sighed. The vibrations of the heart intensified, sending short waves of pleasure through you. You couldn't hold back any longer, letting out soft 'oh's. Mettaton's head lowered, bending over take you in. You stopped looking at this point. All you know is you could feel his teeth scraping along your other thigh, both the heart and his mouth creeping their way towards your privates. The heart reached there first, the vibrations sending you into twisting convulsions of pleasure. Your moans grew in volume and frequency. You arched your hips, stimulating a moan from Mettaton as well.