Viswamithra comes to take Rama with him on his quest to Sidhasrama in "Rama's Initiation". This reveals that Rama has been chosen because instead of requiring for the king himself he asks for his son Rama. Rama does not have much of a choice becoming a hero because the sage puts him in the situation to become a hero.
In "Rama's Initiation," we learn that Viswamithra comes to take Rama with him on his journey to Sidhasrama. Viswamithra is a sage, and the fact that he went to the king and asked for his son Rama for help to conquer the demon suggests that Rama has been chosen by fate for a special destiny. This is also the characteristic that makes the story an epic, as a hero goes on a journey to accomplish a mission.
