Hercule Barton, occasionally documented as Burton, is a teenage female detective distinguished by violet hair, red eyes, and a slim physique at 156 cm tall and 46 kg. She displays profound shyness and timidness, frequently blushing and speaking with a stutter. Despite her reserved demeanor, she consistently strives to be the voice of reason within her team, though her contributions are routinely ignored, resulting in visible frustration. Her alias "Elly" is widely used among peers.

She wields a supernatural ability called Toys, granting extraordinary physical strength—exemplified by feats like lifting cranes—but exhibits apologetic hesitation when employing it. This power temporarily fades after confrontations with adversaries such as the Phantom Thief Empire. As the most level-headed team member, she contrasts sharply with her eccentric companions.

Subtle romantic or admirational inclinations surface in her interactions, notably forming hearts in her eyes around characters like Kate and Mary, whom she addresses as "Onee-sama." Covertly perverse tendencies emerge through her fascination with censored material and suggestive scenarios involving others. She engages in group activities, including shared sleeping arrangements with teammates.