Daphne Greengrass and the Preemptive Adulterer
Harry doesn't necessarily expect a polite "thank you" after saving Daphne Greengrass and her younger sister from falling to their deaths, but he definitely doesn't expect the stream of verbal and magical curses he gets instead. His surprise is nothing compared to hers when her curse fails, though, and that discovery propels the two into a whirlwind week of legal loophole abuse, awkward lust, and weaponized Pureblood etiquette lessons.