In the anime Tenchi Muyo! GXP, the character known as Erma is not a distinct individual but rather an alias and disguise used by the space pirate Ryoko Balta. Under this assumed identity, she presents herself as a Wau office clerk working within the Galaxy Police organization. This cover allows her to operate in close proximity to the main protagonist, Seina Yamada, without raising immediate suspicion.

The motivations for assuming the Erma persona are tied to Ryoko Balta's activities as a member of the Daluma Guild. Her primary objective in using this disguise is to lure Seina Yamada and his ship, the Kamidake, into space as part of a larger plan. The Erma disguise serves as a tool for manipulation and espionage, enabling her to gather information and create opportunities for pirate operations. Her key relationship in the story is therefore with Seina Yamada, whom she dates under the false identity of Erma. This relationship is built on deception, as she conceals her true nature as a space pirate and namesake of the infamous Ryoko Hakubi.

The development of this character arc reaches a turning point when, during a date with Seina, Ryoko Balta chooses to drop the Erma facade and reveal her true self to him. This revelation is a significant moment, exposing the deception that had been central to her interactions. Following this, it is explained by the character Airi that Erma’s secret identity had been known to certain authorities for some time, and that the disguise was deliberately allowed to continue as a means to draw pirate activity toward Galaxy Police patrols. No notable abilities specific to the Erma identity itself are documented beyond the act of disguise and infiltration.