Cubic Galois is a short-statured middle school student at Root Academy holding the solver title Edison. He has short blonde hair, blue eyes, and wears a white shirt, green tie, light yellow vest, blue trousers, brown shoes, and a distinctive long lab coat. Initially considering numbers his only friends, Cubic disliked puzzles, believing they wasted a genius's time. This changed after witnessing Kaito Daimon solve a POG puzzle using Phi-Brain abilities, sparking an intense interest in Kaito. Though his early demeanor could seem self-centered due to immaturity, he gradually grew more aware of his actions' consequences. He accepts nicknames like "Q-chan" from Nonoha Itou and "Q-taro" from Gammon Sakanoue, reflecting his social integration.

An inventor inspired by Thomas Edison, Cubic frequently creates robotic assistants. After losing his robot Mr. Okabe in England, he developed replacements named Mr. Yoshio and Mr. Iwashimizu. His aptitude for invention and mathematics connects to his name's origin: the Galois group in cubic polynomial theory, named after mathematician Évariste Galois.

In later story arcs, Cubic's prominence diminishes. During conflicts involving the Orpheus Order, he receives minimal focus, appearing in one dedicated episode requiring Kaito's puzzle-solving help and another shared with Ana Gram. He is bypassed as a candidate for Orpheus possession despite his Phi-Brain potential. Cubic maintains a loyal, observant stance toward Kaito, even tracking mundane details like his shampoo usage.