It starts in first year. Y/N is sorted into Slytherin. She’s kind, funny, and somehow completely immune to Draco’s usual arrogance. Instead of being intimidated by him, she rolls her eyes when he’s dramatic. For some reason, Draco likes that. A lot. By second year he’s got a crush. By third year it’s obvious. By fourth year it’s embarrassing. By fifth year it’s become a running joke.