Cubic Galois (also written Cubik Galois) is a student at Root Academy bearing the Solver title "Edison," a nod to his inventive nature. His name originates from the mathematical Galois group for cubic polynomials, paying tribute to mathematician Évariste Galois. He possesses short blonde hair, blue eyes, and a notably short stature reflecting his middle school age. His typical attire consists of a white shirt, green tie, light yellow vest, blue trousers, brown shoes, and a distinctive lab coat underscoring his scientific focus.

Initially, Cubic prioritizes mathematics over puzzles, deeming genius incompatible with puzzle-solving and considering numbers his only companions. This perspective shifts dramatically after witnessing Kaito Daimon's Phi-Brain ability during a P.O.G. puzzle, igniting his interest and forging lasting loyalty to Kaito's cause. Early characterization reveals self-centered tendencies stemming from his youth and limited grasp of his actions' consequences. He accepts the affectionate nickname "Q-chan" from Nonoha Itou without objection, while Gammon Sakanoue occasionally calls him "Q-taro."

Cubic's primary contribution involves creating robotic assistants like Mr. Yoshio and Mr. Iwashimizu, developed after losing his initial robot, Mr. Okabe, in England. Direct encounters with deadly puzzles drive his character development. A pivotal moment occurs during a near-fatal confrontation with a puzzle designed by Rook from his childhood, triggering a Heroic BSoD that forces him to recognize the extreme dangers they face. This trauma fuels his maturation from naive overconfidence to a more cautious, team-oriented mindset. He displays competitive jealousy when Kaito focuses on other solvers, reflecting his deepening personal investment.

Throughout the series, he participates in critical missions against the P.O.G. and Orpheus Order, his vital technical skills neutralizing traps and supporting fellow Solvers. In the third season, he travels to England with Kaito's group to restore Jin's memories, navigating underground mazes reactivated by the enigmatic girl Raetsel. His journey marks a transition from isolation to collaborative problem-solving, maintaining his mathematical foundation while integrating puzzle-solving as a necessary extension of his intellect.