Forge nodded as he heard Aiko tell him to keep going; he built up the speed, pounding hard and fast until he could take it no longer. He gave one last hard thrust, pushing himself as far as he could go inside Aiko and spilling a large amount of his seed inside her. He then laid on top of her, panting slightly.
He was about to ask Aiko how she felt when something stopped him; something evil. He then felt.....disconnected. Disconnected from his own body. He saw his vision darken slightly; it was as if he was watching himself move from a third-person perspective. Just then, his mental self looked down and saw that he was chained up. He tried to budge but couldn't move. The Kisha doppelganger then chose that moment to step, sporting a wide, jagged-toothed grin on its face. It then spoke to Forge in its raspy voice, "You know that looks like fun. I think I'll do that with her before I devour her soul." Forge grimaced as he struggled against his restraints to no avail, shouting "You said you wouldn't kill her if I stayed quiet!"
The Kisha's smile grew wider, "Oh, yeah. I guess I did, didn't I? Well, sorry, but I had my fingers crossed." Forge got a confused look on his face, to which the Kisha responded, "It means the deal's off, moron. Now you get to watch as I, or rather you, kill the woman who saved you. Don't worry, she won't even know that you and I switched places. She'll think you're the same adorable amnesiac." Forge struggled ever harder against his chains as the Kisha disappeared to take control of Forge's body.
Back on the outside, Forge, or secretly demon-Forge, was slowly lifting himself off of Aiko and laying on his back. He then looked over at Aiko and said with a smile, "Aiko, do you feel good?"
(Just an FYI, the scene between Forge and the Kisha was all in his head, and they basically "switched minds" and the real Forge is a prisoner of his own psyche. They switched in such a way that Aiko would likely not have noticed the switch take place.)