Joker tasted like pure sin in Batman's tongue. While they kissed Bruce wondered about how he ended up with him like this, not that he was complaining.
How all those nights of passionate fights ended up with him making out his arch-enemy in this raining night?
"You complete me"
"Destined to do this forever" Whispered the wind.
He should have guessed that they would soon end up like this, the Joker knew it before him, and he had tried to show him every time they fought.
"Two sides of the same coin"
They were bonded to each other in a way that nobody will ever be.
Chained to each other; Anarchy and Chaos incarnated within Justice and Order.
And in that heated kiss, they sealed a deal.