Original: Fearful of the heavy responsibilities of the position, and being separated from his beloved mentor Monk Gyatso, Aang flees from home on his animal guide, a giant six-legged flying bison named Appa.
Simplified: Fearful of the heavy responsibilities and the separation from his beloved mentor Monk Gyatso, Aang flees from home on his animal guide, a flying bison named Appa.