"Dark Gathering" is a supernatural horror anime that revolves around a group of individuals drawn together by their shared encounters with the paranormal. The narrative centers on Keitarou Gentouga, a university student with a traumatic past involving a near-death experience that left him with the ability to perceive spirits. This ability attracts the attention of Yayoi Houzuki, a mysterious and highly intelligent girl who is deeply involved in the study of the occult. Yayoi seeks Keitarou's help to investigate and exorcise dangerous spirits, driven by her personal mission to rescue her childhood friend, who has been trapped in the spirit world.

The story unfolds as Keitarou and Yayoi, along with their classmate Eiko Houzuki, Yayoi's older sister, form a team to explore haunted locations and confront malevolent entities. Each episode typically focuses on a specific supernatural case, blending elements of mystery, suspense, and psychological horror. The series delves into the backstories of the spirits they encounter, often revealing tragic or unsettling events tied to their origins. These spirits range from vengeful ghosts to cursed objects, each presenting unique challenges that test the group's resolve and ingenuity.

Yayoi's expertise in occult rituals and her collection of cursed artifacts play a crucial role in their investigations, while Keitarou's sensitivity to spirits provides critical insights into the nature of the threats they face. Eiko, though initially skeptical, gradually becomes an integral part of the team, offering emotional support and a grounded perspective. As the series progresses, the stakes escalate, with the group uncovering a larger, more sinister force at play, connected to Yayoi's past and her relentless pursuit of her missing friend.

The anime balances episodic storytelling with an overarching narrative, gradually revealing the deeper mysteries surrounding the characters and the spirit world. Themes of trauma, redemption, and the consequences of meddling with the supernatural are explored through the characters' interactions and the moral dilemmas they face. The series maintains a tense and eerie atmosphere, with a focus on psychological horror and the emotional toll of confronting the unknown.