Souji Jikukawa holds the positions of student council president and puzzle club president at Root Academy. Initially known as the Solver 'Newton', he failed to attain Phi Brain status during his freshman year. Recruited by the school headmaster into POG (Puzzle of God), he adopts the alias 'Minotaur', acting as a Giver who crafts philosopher's puzzles. In this role, he maintains a false friendship with Kaito Daimon while secretly challenging him on POG's behalf.

His defining trait is constantly drinking boxed apple juice through a straw, which he considers his personal treasure. Abandoning this habit marks a significant shift, signaling his descent into brainwashed antagonism after using a counterfeit Orpheus armband supplied by POG. This device manipulates his actions to align with the organization's goals.

Following his exposure as Minotaur, further deception emerges revealing his affiliation with the Orpheus Order. This group believes the Orpheus armbands facilitate human evolution and opposes Kaito for rejecting his own armband's influence. Souji's connection to the Order represents an escalation in his antagonistic role beyond his initial POG activities.

After the events of the first season, his narrative presence significantly diminishes, with later seasons substantially reducing his role. The character does not appear in any subsequent official media beyond the main series.