Accio_Sriracha_
Draco Malfoy could name all of the things he cared about in the world on one hand. And, well, it isn't his fault that Potter happened to take about three of those slots.
Furious by Potter's numbness after the war, Draco does everything he can to try to bring him back to the way that he was, to his old, happier, self.
As a last resort, Draco does the only thing he's ever known to do when it comes to Harry Potter.
He fights with him.