My idea is that Draco is doing bad in his subjects so he is assigned a tutor, no one in the upper years or his year wants to do it so a smart ravenclaw from the year below volunteers to do it (Luna). She has hidden feelings for Draco that started off as a crush, similar to Ginny with Harry. Draco doesn't return these feelings for a while but about a month later he starts to feel something for Luna that he has never felt before.