After had defeated the Dark Lord, students back to Hogwarts to finish their study, so do 8th year students

But because the school has been destroyed a lot from the battle, 8th year students have to share room to have enough space

Harry Potter, somehow, being roommate with his enemy, Draco Malfoy

"Oh seriously? How can I go through this year living with Malfoy"

Harry pissed off and thinks to himself. But due to that, Harry knows more about his enemy's secrets, even dark ones