Annoyed by the never-ending deluge of date invitations for Valentine's Day, Fleur is out of patience and simply asks the one person seemingly unfazed by all the madness going on around them. Harry. So Harry was just walking down some random corridor when Fleur pops out of nowhere, tells him that he's her Valentine's date and leaves before he can find the wits to ask a question. So Valentine's day comes around and Harry is 90% sure that Fleur was just joking, but a small part of him hopes that she wasn't, which is why he shows up at the meeting spot under his invisibility cloak and only pulls it off once he sees Fleur. They have a quick chat where Fleur explains her motivation while they drive down to the village, which leaves Harry confused. They have a lovely day exploring the village for date spots which aren't the Three Broomsticks or the tea shop. Maybe a light picnic. Fleur confesses her fear of the second task (human hostage rather than fetching an object) and Harry offers that they do the task together since he does not care about winning. He also elaborates on why Moody's "to kill him" might not be paranoia speaking given what else has happened at Hogwarts. Then the second task comes along and they have to fight their way through hordes of sea creatures together. Maybe end it similar to canon with Fleur kissing Harry as a thank you at the end, only here it would not be platonic at all.