When we are first introduced to Haru in "Imprisoned", he is practicing his Earthbending in secret, because if he is discovered Earthbending, he will be taken away like his father. When he uses Earthbending to save a man, the man tells the Fire Nation and Haru is taken away. Katara then fakes Earthbending, to get arrested and save Haru. She manages to inspire the Earthbender that have been stranded, and they rebel and escape.
Haru reappeared reacently yet again for the Invasion, having grown a moustache. He takes part in the Invasion, and later he escapes with the other kids on the back of Appa. He currently resides with the rest of the gang in The Western Air Temple.
Haru is an Earthbender, and learned how to use his ability from his father.
Haru Tries to ask Aang to help him try to escape his father from a fire nation ship. Aang strongly help's him. As they move up to the fire nation ship they sneaked in. While Aang, Haru, and Sokka thinks up a plan Katara gives an inspirational speech to the earthbender prisoners. While the speech was happening Haru and Sokka thought up a plan of using charcoal as there weapon. While the prisoners gave up hope Aang airbends a whirpool like machinegun and loads it up with charcoal and started attacking the fire nation. Thats when the prisoners gain hope and attacked. It didnt took long enough to conquer the ship and release Haru's father