Hikari, known as Dawn, is a Pokémon Coordinator from Twinleaf Town in Sinnoh, aspiring to become a Top Coordinator like her mother, former Top Coordinator Johanna. She began her journey with a Piplup from Professor Rowan, which serves as her primary partner. A childhood electric shock from Plusle and Minun caused a lasting fear of them and earned her the nickname "Dee Dee" due to her sparking hair.

During her Sinnoh journey, Hikari developed innovative contest strategies including "Flame Ice" (Cyndaquil's Flame Wheel encased in Mamoswine's Ice Shard) and "Ice Chandelier" (Pachirisu's Discharge within Buneary's Ice Beam). Her Mamoswine initially disobeyed after evolving, but persistent trust-building resolved the issue. She earned five Ribbons to qualify for the Sinnoh Grand Festival, reaching the finals before losing to rival Zoey. This reinforced her independence, leading her to return her mother's good-luck Ribbon as a symbol of forging her own path.

In the Unova-based "Rival Destinies" arc, Hikari appears as a guest competitor in the Pokémon World Tournament Junior Cup. She battles Iris using Mamoswine against Iris's disobedient Dragonite, demonstrating refined coordination skills as her Mamoswine follows commands precisely. After defeating Iris, Hikari offers advice based on her past struggles, emphasizing patience and mutual trust to overcome a Pokémon's stubbornness. She later battles Cilan to a tie and departs Unova to compete in Johto's Wallace Cup.

Her expertise extends beyond battles; she assists others in understanding Pokémon behavior, sharing insights with Iris about handling headstrong Pokémon. Her strategies, like the Counter Shield technique, have influenced other trainers' battle tactics. Hikari's development reflects a continuous focus on perseverance, innovative contest performances, and mentorship.