In the beginning of the Pokemon series, there was a trainer named Red...or Blue...or Ash...or, basically, whatever you decided to name them, since really they didn't have a name of their own. And by the end of that journey, they were the Pokemon champion. So what's left? What mountains are there to climb? What kingdoms are there to conquer?
Perhaps there were none - so the trainer that you named just continued to wander, endlessly battling Pokemon til the end of his days - since it was the only thing he ever truly knew.