After being disowned by her conservative parents because of her insistence on the legendary "Mare in the Moon," the yearling blank-flank Karateka is ready to end it all. As she is about to bring her existence to a close, she is suddenly rescued by the closest pony she could call to a friend, the mare in the moon herself, Princess Luna. Luna takes the young pegasus in under her wing and gives Karateka a reason for living. In payment, Karateka vows to return the favor, but being the Princesses' personal guard may be a lot harder than any pony originally thought.