My idea:

I once lived in a village by Mt. Paozu.  When I was 3 a meteor crashed into the mountain and after that we started hearing about the monster of the mountain, a giant ape that went on a rampage every full moon.  When I was fourteen I was hunting when my village was destroyed by this monster.  I sought out the famous Turtle Hermit so that I could defeat this monster and get justice for my people.