Leona is a childhood friend of Dawn and Kenny, and she also sometimes calls Dawn Dee Dee (Japanese: ピカリPikari). She lives near a hot spring with her parents and takes care of three Swinub.
In Hot Springing a Leak!, Leona had the water from her hot spring stolen by someone. She later found out that Team Rocket was siphoning the water from her hot spring's main pipe, planning to use it to start their own hot spring. Later, she and Dawn defeated Team Rocket and returned the water to her own hot spring. When she parted ways from Dawn, Ash, and Brock, Leona told them that she would go and battle in Sinnoh's Gyms. It is unknown if she has any Badges yet.
Leona has a similar character design to that of Kenny, having similar hairstyles and clothes, and also being Dawn's childhood friend. Both also call Dawn "Dee Dee" sometimes.
Leona is also similar to Peggy, who appeared in Spring Fever, because she has three Swinub in her possession and runs a hot spring. The only slight difference is that Peggy was still building her own hot spring with her father.
Dawn, who is notably Leona's best friend, would later go on to capture her own Swinub, the only Pokémon Leona has.
Leona's Japanese name comes from 湯もみ Yumomi, a traditional method of cooling down hot spring water using wooden paddles.