Frosch is an Exceed, an anthropomorphic cat species, and a Mage of the Sabertooth Guild, once hailed as Fiore's strongest guild. This small, green-furred cat stands on hind legs, sporting a long tail, large round eyes with prominent lashes, and rosy cheeks. Nearly all features are concealed by a distinctive pink frog suit patterned with black spots, featuring a plain belly, webbed hands, and a hood forming a frog's head with beady eyes. Frosch wears this costume daily due to a mistaken belief about being a frog, even gifting a similar suit to Rogue.

Frosch maintains a perpetually cheerful outlook and speaks exclusively in the third person. The character readily agrees with others and often poses questions peers find redundant. A deep fear of excommunication from Sabertooth exists, though Rogue's steadfast presence provides constant reassurance. Frosch forms powerful bonds, especially with Rogue, reacting with profound distress to Rogue's peril or injury. This protective drive leads Frosch to confront threats like Gajeel when the entity "Shadow" possesses Rogue. A close friendship thrives with fellow Exceed Lector, marked by constant companionship. Frosch plunges into intense shock and depression during Lector's temporary disappearance. A positive bond also exists with Yukino; Frosch voices sadness after her excommunication and expresses loneliness.

During the Grand Magic Games, Frosch accompanies Lector to Magnolia to gather intelligence on Natsu Dragneel's participation, reporting findings to Sabertooth. Frosch witnesses Yukino's excommunication, later confiding fears to Rogue about personal weakness leading to dismissal. The character observes Natsu's infiltration of Sabertooth's lodges and the subsequent clash with Jiemma. Throughout the Games, Frosch spectates guild matches, displaying eager smiles during Rogue and Sting's tag battle against Natsu and Gajeel, then visible distress and tears as Sabertooth falters.

A pivotal moment unfolds during Rogue's fight with Gajeel. As Rogue struggles and questions his guild standing, Gajeel highlights Frosch's unwavering friendship. Frosch becomes tearfully touched by Rogue's acknowledgment of their bond. This shifts when "Shadow" possesses Rogue. Confused and frightened by the transformation, Frosch declares unfamiliarity with the entity and later rushes onto the battlefield, determined to reclaim Rogue. After Gajeel defeats the possessed Rogue, Frosch physically shields him, pleads desperately for his safety, and tearfully embraces him upon his return to consciousness.

Future Rogue later reveals a direct threat to Frosch's life, warning that an unidentified individual will kill Frosch within a year and urging protection to prevent this fate.