Your new body knows just what to do. Not that its a significant challenge, as Japhiel is not only dealing with biological instincts he had only understood on a theoretical level as an angel, but he is doing so from the body of a sixteen-year old boy.
You walk towards him, with a sway to your hips and your new tail dancing. He trembles.
You take his hand, and put it on your new breast. He jerks it away, and you patiently capture it again. This time you place it between your legs, and it stays there. You unzip his pants, and pull them down. "What have we here?" you chuckle. "Not such an angel after all." Your new instincts tell you that he likes to be dominated a little, so you push him down on the bed and straddle him. Your physical lusts are temporarily sated as you feel his penis in your factory-issue vagina. Seducing an angel brings you perfect fulfillment as a demonic female. You hear the hellish laughter of your big sister succubus in the background.
You start to siphon the male energy from Japhiel, but the angelic energy is interfering.