Yuki, a young girl living in a quiet rural town, dreams of escaping to the big city to become a painter. She has been diligently studying art with that goal in mind, but her ambitions are put to the test when her older sister decides to leave first to pursue her own dreams. Yuki accompanies her sister to the train station to bid her farewell, but during the ride or while at the station, Yuki is suddenly assailed by a strange and inexplicable phenomenon, blurring the lines between reality and illusion.

This unsettling event draws Yuki into a chilling horror story that centers on an enigmatic elderly neighbor, the Tonari no Jiisan or my old man neighbor of the title. As Yuki navigates her daily life in a town that prioritizes the group over the individual, she becomes entangled in a mystery that defies easy explanation. The narrative weaves together multiple threads, including supernatural horror and science fiction, while also exploring the claustrophobic pressures of small-town mentality and a coming-of-age story about a young woman drifting further into isolation.

The story features a cast of varied and intense characters, all seen through the unnerving mood created by author Nokuto Koike. As Yuki tries to understand what is happening, she discovers that the phenomena she is experiencing may have connections to a corporate or secret research angle, adding a layer of conspiracy to the supernatural events. The plot balances moments of graphic horror with quieter scenes that reveal the flawed hearts of people working both with and against each other, as Yuki struggles to determine if what she sees is a supernatural curse, a scientific aberration, or a shared delusion brought on by the pressures of her stifling environment.