System: Any fantasy roleplaying game.
It takes 10-15 minutes for an average reader to digest 2500 words. In that amount of time, you could be up and running a game session. All you need are this Adventure Seed, your game's rulebooks, and whatever monster and NPC stats your game provides. That and a few players and you're off and running.
When the party comes upon a village, they find it in the grip of an enemy force. But what is really going on out here, deep in the woods?