Alt. ending, post DH. 35 year old Harry Potter has been working as the Defense Against the Dark Arts professor at the Hogwarts school of Witchcraft and Wizardry for nearly a decade now after his short stint as an Auror. Life was somewhat uneventful and repetitive, and he felt himself almost going through the motions as he taught class after class.
But one day at the staff table, Neville mentioned that Headmistress McGonagall was hiring a new Charms Professor from France. And Harry, not really paying attention, asked if it was anyone they knew. And Neville, who was a professional who read the notices from the Headmistress, assumed Harry had too and was joking. So Neville replied with a joking "we'll see".
Flashforward a week and McGonagall assigns Harry to help their newest Professor settle in, telling him to meet her at her quarters and give her a tour of the castle and grounds. Needless to say, but Harry isn't thrilled to meet the new Professor who he assumed was some starry-eyed youngster fresh out of teaching school. So, with lead feet, he strolled as slowly as possible to the new professors' quarters.
Arriving and deciding to get it over with as soon as possible, Harry knocked. And upon hearing a muffled "come in", he entered to find an arse right in front of him.
An extremely nice-looking arse.
The witch was bent over at the waist, digging in a large, ornate trunk and giving quite the show as she jostled things around in her trunk. After a few seconds the witch turned around to reveal a beautiful silvery-blonde witch a few years his senior with an enchanting aura. She eyed him up and down before giving him a knowing look, Harry instantly realizing that she had caught him staring at her arse. Harry was about to apologize when she gave a humored chuckle;
"We 'aven't seen each o'zer in almost two decades and 'ze first 'zing you do is stare at my ass? 'Ow uncouth, 'arry. You should at least ask next time."
Harry's eyes widened, "Fleur?"
Her eyes dazzled with humor, "'Ze one an' only. We're you per'aps expecting a troll?"
They quickly set to catching up as Harry helped her settle in. They travelled the castle and grounds together, with Harry giving Fleur an updated tour of the school she had nearly spent a year at almost 20 years before. But eventually the sun started to set and Harry and Fleur reluctantly parted ways, but not before Harry promised to meet her back at her quarters the next morning to walk her to the Great Hall despite her already knowing where it was.
As the next school year started, harry and Fleur quickly became best of friends, often talking for hours in the Professors' hall or either of their private quarters.
They found themselves helping the other with their lesson plans more often than not, even helping the other go through tests and homework.
But as winter came, Harry felt himself realizing that his feelings for his fellow professor were not merely professional. And, in a bout of Gryffindor courage, asked her to accompany him to the Winter Ball on Christmas Eve. And, surprisingly, Fleur only gave a sly smile before saying that she was wondering when he would ask her.
After an enchanting night, and a heavenly kiss under the mistletoe, they started dating. Winter ended not soon after that, and Spring came and went. And when the professors where readying to leave Hogwarts for the summer, Harry surprised his girlfriend by inviting her to stay with him at Grimmauld Place for the summer. And Fleur, not surprisingly, agreed.
It only took a month into summer break for Harry to ask Fleur to marry him after a breathtaking date in the Scottish Highlands. And Fleur, again not surprisingly, said yes.
And the rest, as they say, was history.
(feel free to extend the prompt as long as you want.)