Sorry to the guy who prefers the short ones, but anyway...
It is, strangely, a science-fiction fantasy. Guy finds a weird back-alley bookstore in the centre of the city (think Gremlins). The even weirder old guy behind the counter offers to sell him a time stop device - a box with a red button. Guy says when you press the button, time stops, except for you. It costs $100, and it can only be used once (and it's not said, but he'll probably never find this shop again). Naturally, guy thinks this is garbage, but he's just received a bonus from work, plus he's found a book that's nearly impossible to find, so he tips weird guy the $100 and takes the box.
If this device is real, probably a sensible time to use it would be a Saturday night. Then he could cruise around town at his leisure, and go to all the bars and clubs feeling up all the hot chicks, and live out his dirtiest fantasies. Like a normal pervert would. But this pervert presses it on a Friday morning. And it only fucking works! Being Friday morning and being a better class of pervert, he can instead go to all the private girls' schools in the posh part of town, and go to the seniors' (18+) classes to find the hottest ones. He picks the school with the biggest sports field, and picks all the hottest senior girls and takes them there and lies them face down in a line. Then he takes the school bus and drives to all the nearby schools and collects all the hottest seniors from each of those schools too. Obviously there's logistical challenges - he can't take a big bus because all the traffic would be stopped on the roads and he'd have to try and weave around it. So he uses golf carts, wheelbarrows, whatever the fuck he can to move the girls. Anyway, he ends up with a field full of fucking hundreds of hot seniors all lying face down in the grass.
Then he can, at his leisure, pull up their skirts, rip off their underwear, grab some lube and sodomize every single one of them. He has all the time in the world. As time goes on he can see his progress pretty easily by the number of exposed peachy bums along the line.
This is a fantasy world he lives in for what would normally be weeks, months, but who knows, because it's always the same time. Anyway, he comes and goes (ha!) over a long time, until one time he comes back and stands and surveys his mighty work - the majestic scene of hundreds of hot chicks' butts he's plundered, and then does a double take. Somewhere in the middle, and he knows he didn't make a mistake in placing them - one of the girls is missing.
What happens next? Think the whole thing would make a good story.
(Obviously the school thing is "skirting" around the limit of the rules on content, so it would be dependent on that being okay. It could be set at a university I guess.)
