Cynthia was first mentioned in Lucian's flashback in An Elite Meet and Greet!, along with the members of the Sinnoh Elite Four.
She properly debuted in Top-Down Training!, where she was first seen battling against Lucian with her Garchomp on television. She then arrived in person in Amity Square, where she was studying ancient tablets. It was here that she met Ash, his friends, and Paul, who rushed down to Amity Square after they heard rumors of Cynthia being there. Paul challenged her to a Full battle, but Cynthia won easily. She then mentioned that she was just like Paul in her youth, determined to win with the strongest Pokémon. After the battle, because Nurse Joy was busy, she and Brock personally healed Paul's Pokémon, after convincing him to take them to a Pokémon Center. After this, back at the Amity Square Ruins, she explained something written there means very much to her: "When every life meets another life, something will be born". Later, Ash would think about this quote from time to time. Cynthia then decided to go to Celestic Town, where she planned to study the legend of Dialga, Palkia, and the Lustrous Orb.