Masataka Hiki heads the Drug Enforcement Division for the Kantō region within Japan's Narcotics Control Department. Thirty-two years old, he shares this age with his colleague Keigo Kajiyama, the department's Chief of Investigations. Hiki consistently displays a cheerful, easygoing demeanor in his professional dealings. This affable exterior contrasts sharply with his operational capabilities, where he displays sharp analytical skills and strong deductive reasoning.

His professional history includes working alongside veteran detective Yoshiaki Saiga roughly sixteen years before the main events, during an investigation into the drug "Switch." This case bore similarities to the later substance known as "Seed" and proved transformative, marked by tragedy that significantly influenced departmental investigative approaches. This experience helped lay the foundation for Hiki's subsequent leadership role and investigative methodology.

Within the organizational structure, Hiki navigates professional dynamics with colleagues like Akimune Narita, a detective from the Meguro Police Department. Narita serves as a departmental rival to the Narcotics Control Department, frequently competing over jurisdictional control or investigative breakthroughs. Despite this rivalry, Hiki approaches these interactions with his characteristic relaxed disposition.

Hiki's family background reveals he is the father of Hal Kurabayashi, one of the primary investigators under his command. This familial tie informs their professional dynamic within the department, though their personal dynamic remains unexplored.