Start with action
Beginning in medias res, as in starting the narrative in the midst of action, is a technique used by masters, such as Shakespeare or Homer, and it is also a powerful tool in your user story arsenal.
At the beginning of The Odyssey quite a few unruly men want to marry Telemachus' mother, while his father has still not returned home from the Trojan War. There is no lengthy introduction explaining how those men ended up in Ithaca, or why the goddess, flash-eyed Athena, cares about Odysseus.
The poem was composed in an oral tradition and was more likely to be heard than read at the time of composition. While literacy has skyrocketed since Homer's time, you want to tell and discuss your user stories. Therefore, you should consider a similar start (maybe not mentioning the user's mother or her rascally suitors).