"Dark Blue" is a psychological thriller anime that explores themes of identity, memory, and the blurred lines between reality and illusion. The narrative centers around Aoi Minase, a high school student who begins to experience strange and unsettling visions after a traumatic incident. These visions are tied to a mysterious phenomenon known as the "Dark Blue," a shadowy force that seems to manipulate the perceptions and memories of those it touches. As Aoi delves deeper into the mystery, she discovers that the Dark Blue is connected to a series of disappearances and deaths in her town, all linked to a secretive research project conducted years ago.

Aoi's journey intertwines with that of Kaito Tachibana, a transfer student with his own troubled past. Kaito possesses fragmented memories of the Dark Blue, which he struggles to piece together. Together, Aoi and Kaito uncover the truth about the project, which involved experiments on human consciousness and the creation of artificial memories. The experiments went awry, resulting in the creation of the Dark Blue as a sentient, malevolent entity that feeds on the fears and regrets of its victims.

The series introduces a supporting cast of characters, each with their own connection to the Dark Blue. These include Rina Shirakawa, a classmate who becomes a target of the entity, and Professor Haruto Saito, a former researcher involved in the project who now seeks redemption by helping Aoi and Kaito. As the story progresses, the line between reality and illusion becomes increasingly blurred, with characters questioning their own memories and identities. The Dark Blue manifests in various forms, often exploiting the deepest fears and insecurities of its victims, leading to intense psychological confrontations.

The plot builds toward a climactic confrontation with the Dark Blue, where Aoi and Kaito must confront their own traumas and make difficult choices to stop the entity's spread. The resolution is bittersweet, with sacrifices made and questions left unanswered, reflecting the series' exploration of the fragility of human memory and the consequences of tampering with the mind. "Dark Blue" is a tightly woven narrative that combines psychological tension, mystery, and emotional depth, making it a compelling entry in the psychological thriller genre.