The only way for that to happen is that they somehow get into an accident or smth, both loose their memories, and then get to know each other as lovers. Like you can't be srsly asking for that knowing it would be fake and after all you've done so openly
Even if they both lose their memories, I bet he’ll start fantasizing about killing her to make it fresh and new so he’s psychopathy stays well and alive.
The only way for that to happen is that they somehow get into an accident or smth, both loose their memories, and then get to know each other as lovers. Like you can't be srsly asking for that knowing it would be fake and after all you've done so openly