Hermes serves as a talking motorrad and Kino's primary companion. His core purpose is providing high-speed transportation, requiring a rider for direction and balance, creating a symbiotic relationship. He consistently exhibits a personality of pessimistic realism, frequent complaining, and occasional naive literal-mindedness, traits that create comic contrast with Kino's demeanor. Despite this, he proves steadfastly reliable as both a vehicle and Kino's sole confidant for her inner thoughts.

He possesses high, literal intelligence focused on data and complex physical assessments, though his explanations often remain vague; he once accurately calculated the thrust needed for a mythical flying machine to achieve flight. Pragmatically, Hermes expresses no inherent loyalty to any specific rider beyond the functional necessity of having one to operate. He would simply await another traveler if Kino became unable to ride, a reality Kino understands and actively works to prevent by protecting both herself and Hermes from theft or damage.

Physically modeled after the iconic Brough Superior SS100 motorcycle, renowned for its early 20th-century engineering and speed, authentic sounds from this real-world model were recorded for anime adaptations. His name references the Greek god Hermes, with the narrative specifying the "H" is silent.

In the spin-off "Gakuen Kino," his form changes to a cell phone strap: two canvas strips connected by a brass buckle, featuring an engraved image of the Brough Superior SS100, while his core personality remains consistent.