Sōji Jikukawa balances his duties as Root Academy’s student council president with membership in the puzzle club and a clandestine role in POG’s "Section φ(Phi)" under the alias "Minotaur." Initially aspiring to become a Phi Brain Child, his rejection by the Orpheus Armlet redirected his ambitions toward mentoring Kaito Daimon, the protagonist he views as inheriting his unrealized potential. Recognized by POG’s Kaido Baron for his skill as a "Giver"—designing intricate puzzles to test Solvers—Jikukawa operates discreetly, offering Kaito strategic guidance, logistical support, and analytical expertise during challenges.

Born into a wealthy family with POG-tied parents, Jikukawa’s early pursuit of status within the organization pivoted after his rejection. He conceals his dual identity as Minotaur from peers, including Kaito, while cultivating a reputation as a paradoxically aloof yet approachable figure, respected for subtly guiding underclassmen. His alias "Newton," tied to a preference for apple juice, hints at his intellectual persona.

During the second season, manipulation by a counterfeit "Minotaur" lures him into wielding a replica Orpheus Ring, forcing a temporary alliance with the Orpheus Order. This culminates in a high-stakes puzzle duel against Kaito atop a rigged mountain. Though briefly consumed by the ring’s influence, his defeat shatters its control, reaffirming his loyalty and resilience against external manipulation.

By the third season, Jikukawa enrolls at Root University, formally joining POG and transitioning from shadow mentor to active operative. His arc resolves in harmonizing his dual talents as Giver and Solver, channeling ambition into fostering Kaito’s growth while grappling with POG’s moral ambiguities. Throughout, his concealed vulnerabilities and calculated secrecy underscore a complex equilibrium between leadership, ambition, and unspoken camaraderie.