From Bulbapedia, the community-driven Pokémon encyclopedia.
(Japanese: ヒカリ Hikari) is a ten-year-old girl travelling through Sinnoh with Ash and Brock. Her goal is to become a great coordinator like her mother, Ayako. Her first Pokémon is a Piplup. She is voiced by 豊口めぐみ Megumi Toyoguchi in the Japanese verison.
Like Ash, she is lucky enough to have seen a legendary Pokémon, an Emrit in Begin! From Futaba Town to Masago Town!!.
She had a bicycle, but like Misty's and May's bikes, Ash's Pikachu destroyed it with its Thunderbolt. Ayako gave her one of her old ribbons from her days as a coordinator as a gift for luck. She also had a large suitcase full of dresses, but her mother made her leave it at home due to its impracticality.
Like May, she has her own theme song, 君のそばで 〜ヒカリのテーマ〜 By Your Side ~Hikari's Theme~, the first ending of the Diamond & Pearl anime. The song is sung by グリン Grin.
This listing is of Hikari's Pokémon as of the most recent Japanese episode:
Her Japanese name means 光 Light.
May, Misty and Hikari are girls who travel or used to travel with Ash Ketchum. All of them have Japanese names including the katakana カ ka and dub names starting with M, so some fans believe Hikari will have a dub name starting with M.
On Bulbagarden forums