Shirona is a League master and the Champion of the Sinnoh region in Pokémon Diamond and Pearl and Pokémon Platinum. Other than the player using a female character, she is the first known female Pokémon League champion in the video game series. Her japanese name means "Chosen by the gods"
She has blond hair and wears black clothing. She also has two hair clips that resemble Lucario's Aura Sensors somewhat, but with a yellow stripe instead of being all black. Shirona is from Celestic Town in the Sinnoh region. Apparently she made the training of Professor Rowan when she was young.
In the Anime
Cynthia was first mentioned in Lucian's flashback in An Elite Meet and Greet along with the others members of the Sinnoh Elite Four. She made her first appearance in Top-Down Training!. Her Japanese voice actress is Tomo Sakurai and her English voice actress is Emily Jenness. Internationally, she is played by Samira Fernandes in the Brazilian Portuguese dub.
She was first seen battling against Lucian with her Garchomp on television. She then arrived in Amity Square where she was studying ancient tablets. Paul then challenged her to a battle. She defeated four of Paul's Pokémon using only her Garchomp.
She reappeared in DP096 and DP097 where she tried to stop Team Galactic from stealing the Lustrous Orb.
She has been seen battling and defeating Aaron in DP100.
In Pokemon (2019), it is revealed that Cynthia is the second strongest trainer in the Pokemon World Championships. During the Masters Eight Tournament, comprising of the top eight strongest trainers in the world, she battles and defeats Iris, the Champion of Unova, in the first round. Intending to retire from battles after the tournament, she is paired against Ash in the second round and suffers her first on-screen loss, which inspires her to continue battling.
In the Games
Cynthia helps the main character against Team Galactic in a point in the game. She is also found on Route 214 after the player has defeated Crasher Wake and received the Fen Badge. She gives the player the SecretPotion to get past the Psyduck group on Route 210. She is very interested in mythology and history, and spends her time exploring various sites associated with Legendary Pokémon of the Sinnoh region.
Later, she reappears as the League Champion.
In the Manga
She first appeared in Eterna City just after the trio's starters evolved. She lent them some help before the Gym challenge. She later appears after Platina's Gym challenge in Pastoria City to help some injured Psyduck.
"One look at you tells me many things about you. Together, you and your Pokémon overcame all the challenges you faced, however difficult. It means that you've triumphed over any personal weaknesses, too. The power you learned... I can feel it emanating from you. That's enough talking. Let's get on with why you're here. I, Cynthia, accept your challenge as the Pokémon League Champion! There won't be any letup from me!"