It's a great origin story for a spooky monster. Not just Kevin himself, but the donor corpse too: a flayed ghost haunting the surgeons to get his skin back. He makes his way to the Tranch, sees what's been done to his skin, and then rips it back out of Kevin and they go back to his grave and the afterlife together. "Tee hee if you think about it, you've been inside me already uwu" says Kevin's ghost as they descend.
Or he's so repulsed that he decides he doesn't want the skin back after all and he kills himself or dies of shock, and then some metaphysical horror happens when a ghost dies. Maybe he gets caught in a cycle of rebirth and suicide, reborn as a troon and forever trying to move on into a new life. Get Clive Barker on it, he'd do a suitably gross job of the story.