"Gakkō no Kaidan" is a horror manga series that revolves around supernatural occurrences in a school setting. The narrative centers on a group of students who encounter various ghostly phenomena within their school, which is rumored to be haunted. The story begins with the protagonist, a high school student, who becomes aware of strange happenings after hearing about the school's dark history. As the students investigate, they uncover a series of tragic events tied to the school's past, including deaths and disappearances, which have left lingering spirits.

The main characters include the protagonist, who is often skeptical but becomes deeply involved in the supernatural investigations, and their close friends, each with distinct personalities and roles in uncovering the mysteries. One friend is particularly knowledgeable about urban legends and ghost stories, providing crucial information that helps the group navigate the dangers they face. Another character is more cautious and often serves as the voice of reason, while another is brave and impulsive, frequently putting themselves in harm's way.

As the story progresses, the group encounters various spirits, each with their own backstory and reasons for haunting the school. These spirits range from vengeful entities seeking retribution to lost souls trapped in the mortal world. The students must solve the mysteries behind each haunting, often involving uncovering hidden truths about the school's history and confronting their own fears. The narrative is structured around episodic encounters with different ghosts, each contributing to a larger overarching mystery about the school's dark past.

The manga blends elements of horror, mystery, and psychological tension, with a focus on the students' interactions and the evolving dynamics within the group. The school itself serves as a central character, with its eerie atmosphere and hidden secrets playing a significant role in the story. The series explores themes of fear, courage, and the impact of past traumas, as the characters are forced to confront both external supernatural threats and their own inner demons.

Throughout the series, the students' investigations lead them to uncover a deeper, more sinister force at work within the school, hinting at a larger conspiracy or curse that ties all the hauntings together. The climax involves a final confrontation with this overarching evil, requiring the group to use all the knowledge and courage they have gained throughout their experiences. The resolution of the series addresses the fates of both the students and the spirits, providing closure to the various storylines while leaving room for lingering questions about the nature of the supernatural.