Astin was Jessie's childhood crush and a character of the day who appeared in Crossing Paths. Astin also has a present-day lookalike by the name of Austin. His name is not mentioned in the Japanese version.
Astin used to go to the same school that Jessie was in. He left to become a Pokémon Coordinator and, before leaving, asked Jessie to join him on his journey. Jessie was torn between traveling with her crush and staying at school for her debut as a dancer. Jessie ultimately decided to stay at school and has not seen him since his departure.