Part of the story is this really epic romance between The Joker and Harley Quinn. It’s a fascinating love story because is it love-love? Is it love-hate? There’s a lot of ways to argue what that relationship is and what it means.
Why is The Joker obsessed with her? Does he love her? If he did, could he admit that? I think those are some of the mysteries that are going to be left up to the people watching this film to make those decisions themselves.
— David Ayer on Joker and Harley (x)