Fleur is an aspiring online cosplay model, and Harry is her cameraman/prop-maker
It started normally, Fleur liked video games and big swords, so she asked Harry to make her one out of foam. From there it turned into a suit of skimpy foam armor, then taking pictures of her to post to her tiny, personal Instagram. Next thing they knew, her cosplay photo blew up! And Fleur became obsessed and begged Harry to make her more costumes and props, and also take pictures of her in 'tasteful' outfits. Harry, of course, said yes.
There you go, that's the prompt. Maybe add some funny moments when these two old friends have to get over shyness? Haven't given this one much thought.