After the war, Harry doesn't know what to do. Before, he had had Voldemort to worry about, not to mention the safety of everyone in his hands. Now that Voldemort's gone, he has no reason to keep going. He feels useless, not protecting anyone. He decides to go back to Hogwarts to finish his seventh year, where he may just find his reason to survive.
After his trials to prove his (semi-)innocence, Draco is made to go back to Hogwarts. Hopelessly afraid, he stays to himself, never wanting to cause trouble. All he needs, whether he admits it or not, is someone to care for and protect him from himself. And maybe he will find that person at Hogwarts.
Disclaimer: I do not own Harry Potter or anything, and I'm going to put some references!