"Otogi no Machi no Rena" is a supernatural mystery manga set in a small, secluded town where strange occurrences and urban legends are part of everyday life. The story centers on Rena, a high school girl who possesses the unique ability to see spirits and supernatural phenomena. Her life takes a dramatic turn when she encounters a mysterious boy named Kōichi, who claims to be a "spirit detective" tasked with investigating the town's paranormal activities. Together, they form an unlikely partnership to uncover the truth behind the town's eerie legends and the dark forces at play.

The narrative unfolds through a series of episodic cases, each delving into a different urban legend or supernatural mystery plaguing the town. Rena's ability to perceive spirits becomes crucial as she and Kōichi investigate haunted locations, cursed objects, and malevolent entities. As they dig deeper, they uncover a web of interconnected events tied to the town's history, revealing that the supernatural occurrences are not random but part of a larger, more sinister scheme.

Key characters include Rena, whose empathy and determination drive the investigations, and Kōichi, whose enigmatic past and knowledge of the supernatural provide critical insights. Supporting characters, such as Rena's classmates and townsfolk, often become entangled in the mysteries, adding layers of complexity to the plot. The series balances moments of tension and horror with themes of friendship, trust, and the struggle to confront one's fears.

As the story progresses, Rena and Kōichi uncover the existence of a powerful entity manipulating the town's supernatural phenomena. This entity's motives and origins become the central mystery, leading to a climactic confrontation that tests the duo's resolve and forces them to confront their own vulnerabilities. The manga explores the blurred lines between the human and spirit worlds, emphasizing the consequences of meddling with forces beyond human understanding. Through its blend of mystery, horror, and character-driven storytelling, "Otogi no Machi no Rena" offers a compelling exploration of the supernatural and the human spirit.