Sonia first appeared in GF002, meeting Lexi alongside her grandmother, Professor Magnolia. Lexi confided in Sonia about Zacian and the vision she saw, which peaked Sonia's interest as she'd been studying the history of Galar since college and a mysterious event called "The Darkest Day". Because of this, Sonia decided to have regular catchups with Lexi to see if she discovered anything else during her travels, along with passing on anything she new of. She also helped Professor Magnolia with her research into Dynamaxing, including putting her own Greedent up for experimentation.
In GF064, Professor Magnolia retired her Professor title to Sonia, making her Professor Sonia.
Sonia's research came to a climax when she discovered that the Darkest Day correlated to current day events, with Zacian and Zamazenta being the "heroes" within the story. She and Marlon also became quite close in the research, resulting in Marlon joining her at the Research Lab.