Jin Makata, known as "Youth X," served as a pivotal mentor and guide to protagonists Kaito Daimon and Rook Banjou Crossfield during their childhood, profoundly shaping their early puzzle-solving development. His true identity remained concealed before later revelation.

His name originates from the Japanese term "魔方陣" (Mahoujin), meaning "Magic Square," reflecting his deep connection to intricate puzzles. Physically, he possesses short, messy brown hair, brown eyes, and distinctive small glasses.

Jin's history intertwines with the secret organization P.O.G. (Puzzle of God), where he worked as a recruiter scouting potential Phi Brain candidates. His global travels to hone his skills for confronting the ultimate "Puzzle of God" led to a catastrophic encounter with Count Pythagoras. This resulted in the entity Orpheus being forcibly downloaded into Jin's brain. To contain the threat, Jin psychically sealed both his consciousness and Orpheus within his mind, triggering severe memory loss that erased his past identity and connections.

After the sealing, P.O.G. held Jin captive, isolating him from his former life. Though memory loss obscured his bonds with Kaito and Rook, fragments of their shared past lingered as a latent influence.

During the third season, Jin regained his suppressed memories. This awakening also revived the dormant Orpheus entity, which overpowered Jin's consciousness to seize control of his mind and body. This transformation shifted Jin from victim to instrument of Orpheus's schemes, altering his role in the conflict. His restored memories revealed connections to additional figures: a mysterious girl named Raetsel and a man called Enigma, both linked to his past and his ambition to eradicate all puzzles.