"Tokumu Sōsakan Rei & Fuko" is a supernatural mystery anime centered around Rei and Fuko, two special investigators tasked with solving paranormal cases. The series is set in a world where unexplained phenomena and supernatural occurrences are commonplace, and the duo works for a secretive organization dedicated to addressing these anomalies. Rei, a calm and analytical investigator, possesses a deep understanding of the occult and often relies on logic and deduction. Fuko, on the other hand, is more impulsive and emotionally driven, with a unique ability to perceive and interact with spirits. Together, they form a complementary team, balancing each other's strengths and weaknesses as they tackle a variety of cases.

The narrative unfolds episodically, with each case presenting a distinct mystery involving ghosts, curses, or other supernatural entities. The investigations often delve into the personal histories of those affected, revealing tragic or unresolved events tied to the paranormal activity. Rei and Fuko's methods differ significantly—Rei approaches cases with a scientific mindset, while Fuko relies on intuition and her spiritual connection. This dynamic creates tension but also drives their success in uncovering the truth behind each case.

As the series progresses, overarching elements emerge, hinting at a larger conspiracy involving the organization they work for and the true nature of the supernatural forces they encounter. The relationship between Rei and Fuko evolves, with moments of camaraderie and conflict highlighting their contrasting personalities. The series balances standalone episodes with a gradual buildup of the central mystery, keeping the narrative engaging while exploring themes of loss, redemption, and the boundaries between the living and the dead. The characters' development is intertwined with their cases, as they confront their own pasts and the ethical dilemmas posed by their work.