Momotarō is a genetically engineered flying squirrel esper and key operative within the antagonistic organization P.A.N.D.R.A. As the sole survivor of Japanese military experiments designed to create animal-based esper soldiers, he bears physical modifications including a light bulb embedded in his back—concealed during hibernation—and a crosshead screw implanted in his forehead. His yellow fur and black eyes remain consistent across depictions.

His personality varies between adaptations: the anime presents a cheeky, cheerful demeanor, while the manga depicts a less easygoing, more short-tempered individual. Both versions share his fondness for pranks, often targeting P.A.N.D.R.A. leader Kyousuke Hyoubu, and his affinity for the esper trio "The Children," particularly Kaoru Akashi. Despite possessing human-level intelligence and telepathic communication, he retains animalistic traits like a preference for sunflower seeds and attraction to female squirrels.

Memories of his traumatic military experimentation can trigger uncontrollable rage, causing indiscriminate attacks against allies and enemies alike. This instability drives his character development and adds complexity to his P.A.N.D.R.A. role.

His esper abilities encompass:
- **Aerokinesis**: Generating powerful air blasts for combat, visualized as purple energy beams in the anime.
- **Telepathy**: Primarily used for communication, but capable of immobilizing targets with thought waves for limited durations.
- **Precognition**: A low-level ability allowing him to foresee events seconds ahead, demonstrated when anticipating movements like Aoi Nogami's teleportations during pursuits.

His relationships center on loyalty to Hyoubu and a genuine fondness for Kaoru Akashi, creating narrative tension given P.A.N.D.R.A.'s opposition to B.A.B.E.L., where "The Children" operate. Episodic content, such as anime episode 20, explores his interactions beyond combat roles.