You are feeling agonizing pain radiating into your body through your sphincter. You are a masochist though, and being able to transition pain into pleasure; you find it even more enjoyable as your demonic self is apparently as skilled with the monster between his legs as you were. Although there is no gentle-ness in his touch; the brutal thrusts into you find all the right spots regardless; bestial and painful; but generating just as much pleasure in you as it does pain. Snarling your demonic self bites deep into your shoulder; continuing to fuck you harder and harder. You moan and mewl like a bitch in heat; feeling so wonderfully full. You don't notice as a strange black oily substance begins to spread up your body; covering you slowly and surely; wherever it touches your flesh you melt into sensations of pleasure. You can't stop yourself as you melt more and more into the glorious raping of your hole. All the while your own cock is thrust forcibly into the green haired boy's mouth.
As the black oily substance consumes your flesh you feel yourself drifting away. As only your cock is left uncovered you explode into the boy's mouth and as he pulls away you coat his face in your jizz... just as your cock is developed; and as you are fully consumed in the strange black inky substance your form struggles in the goop and then as the demonic you roars in ecstasy; your old form begins to shrink; and opening at the end of the now shifting and shrinking murky bubble begins to spill out thick creamy white fluid. The green haired boy near your clawed giant feet; as you are the demon now; looks up and watches with a grin as the old you is changed into about three feet of thick dribbling black horse cock. It was strange too because in a way the old you still exists; unable to be aware of anything, but the constant regular dribbling of the contents of it's sack; and the consistent and driving need to be inside something warm and tight.
The new you feels the same powerful need to drive himself into the boy; to be whole with him and claim him as your own; to be his as well. You want to rape him just as you raped yourself. You know he'd like it; you'd be more gentle of course; you actually want him to feel some pleasure; more so than you did yourself; you wished to consume your old self after all. The boy appears to be prepared though as you shoot down to snatch him up; leaping away to the side with a body roll and already beginning with another chain of gestures.