Aaron lived in ancient times and had the power to control the Tree of World's Origin where Mew lives. Rin realized that he had the power to do so and was grateful that his sacrifice to protect her kingdom was not in vain as the hatred and anger that shrouded the land subsided after he activated the tree's calming powers. Aaron became known as the "Hero of the Wave." He recalled his Aaron's Lucario into his staff before he went to the Tree of World's Origin on his Pigeot.
Aaron was known as a "Wave user" and he arrived at Aldoran Castle with Aaron's Lucario where he taught it how to be a wave user as well. Aaron's Lucario later found out through a time flower that Aaron sacrificed himself to protect the kingdom and that he had one last wish which was to meet Aaron's Lucario once again.