The Ghost of Kyoshi (Male Reader X Avatar)

A boy raised on the run with his mother, away from the Fire Nation. His father, a Fire bender who is head of a clan of killers, and his mother, a former Kyoshi Warrior. The boys mother was originally tasked with killing the clan's leader but ended up falling for him and bearing 2 children. Once the father found out about the mothers original plan, he had her chased out of the Fire Nation and into the Earth Kingdom while she was pregnant with their second child.
After about 12 years of running, the women's second child, her son, disguised himself as his mother with her Kyoshi warrior garb and lead the chase of assassins away from his mother for two years where he eventually crosses paths with the Avatar. Along this journey, he learns the secrets of his heritage and how to become one of the most powerful earth benders in history.