Arena Tycoon Greta/Manga/PA/History

Greta is one of the seven s hired by Scott to be a Frontier Brain at the. Greta is first seen hosting the Battle Frontier's opening ceremony. The ceremony is interrupted by, who announces that he wishes to conquer the Battle Frontier. The press mistakenly report the incident as allowing an ordinary Trainer to take part in the Battle Frontier before it officially opens a week later. The Frontier Brains decide to use this assumption as free publicity and allow Emerald to challenge the Battle Frontier under the condition that he completes it before it officially opens.

Later, while Emerald is challenging the Battle Pyramid, Noland is attacked by an unknown assailant and several rental Pokémon are stolen. After Noland is taken to a hospital, the other Frontier Brains begin to suspect Emerald as the culprit. They head to the Battle Pyramid to confront Emerald and find him after having defeated Brandon. When they ask him about what happened, Emerald reveals that he did not attack Noland and is actually after the Mythical Pokémon. The Frontier Brains find Emerald's explanation suspicious, but decide to follow him into Artisan Cave, where Jirachi is currently located at. Upon arriving, everyone is attacked by a horde of wild while Emerald continues inside to find Jirachi. After the Frontier Brains get past the Smeargle, they meet up with Emerald, who has managed to find Jirachi. Emerald attempts to capture Jirachi, but is attacked by Guile Hideout, the actual culprit who attacked Noland.

Emerald is attacked by Guile's stolen rental Pokémon, but he refuses to fight them and continues to head after Jirachi. When Greta sees this, she angrily tells Emerald that stopping Guile is more important than Jirachi and goes off to help the others. When Spenser, Lucy, Tucker, and Brandon are defeated by Guile, Greta steps in to help and defeats the rental Pokémon. Eventually, Jirachi escapes, forcing Guile to leave to continue his pursuit of it. Injured from the battle, everyone decides to return to the Battle Frontier. Upon arriving, the press demand to know where the Frontier Brain's had gone and why they were injured. Tucker lies to everyone that they were all in training and sends Greta to have her battle with Emerald.

At the Battle Arena, Greta is Emerald's fourth opponent, and Emerald is allowed to battle her directly. Both sides fight hard, but Emerald eventually emerges as the victor, earning himself the Guts Symbol in the process. The battle leaves Emerald so exhausted that he and his Pokémon fall asleep. Greta brings Emerald and his Pokémon to the Battle Frontier's accommodations to sleep properly. When Greta and reporter Todd undress Emerald to make his sleep more comfortable, they are shocked to find that Emerald is much shorter than he initially appears. Todd kicks Greta out of the room and asks her to pretend she saw nothing.

The next day, Greta assists the other Frontier Brains in ushering people to the Battle Dome. During the tournament, Guile appears and manages to capture Jirachi. Guile uses the rental Pokémon to the attack innocent bystanders and heads to the to make his wish. Once he arrives at the Battle Tower, Guile uses Jirachi to wish for a gigantic Kyogre made of seawater to flood the entire Battle Frontier. Greta and the other Frontier Brains work together to get civilians to safety and fight off Guile's rental Pokémon while Emerald and the other Pokédex holders fight Guile. Eventually Emerald and the Pokédex holders manage to defeat Guile and destroy the gigantic Kyogre monster. The day after, an injured Greta and the other Frontier Brains congratulate Emerald for the hard work he put into saving everyone.

Greta and the other Hoenn Frontier Brains battle and defeat the Admins of Neo Team Magma and Neo Team Aqua, who had interfered in the launch of a rocket that was made to stop the meteoroid threatening to destroy the world. Greta attempts to interrogate the Admins on the location of their accomplice, Zinnia, only for the Admins to deny knowing where she had gone.