"Circle Sākuru" is a psychological thriller manga that explores themes of identity, memory, and the consequences of technological advancement. The narrative centers around a mysterious online game called "Circle," which promises players the ability to relive their memories and alter their past. The game's enigmatic creator, known only as "Sensei," claims it can help users confront unresolved trauma and regrets. However, as players delve deeper into the game, they begin to experience disturbing side effects, including memory loss, identity confusion, and even physical harm.

The protagonist, a young man named Kaito, becomes entangled in the game after his childhood friend, Rina, disappears following her participation in "Circle." Determined to uncover the truth behind her disappearance, Kaito joins the game and discovers a surreal, dreamlike world where players' memories are reconstructed in fragmented, often distorted ways. As Kaito progresses through the game, he encounters other players, each grappling with their own regrets and secrets. Among them is Aya, a woman searching for her lost sister, and Tetsuo, a former scientist who claims to have insider knowledge about the game's origins.

The plot unfolds through a series of interconnected storylines, revealing the dark underbelly of "Circle" and its creator's true intentions. Sensei's motivations are gradually unveiled, exposing a complex web of manipulation and experimentation. The game's mechanics, which involve extracting and manipulating players' memories, raise ethical questions about the boundaries of technology and the human psyche. As Kaito uncovers more about the game, he must confront his own past and the unresolved guilt surrounding Rina's disappearance.

The manga's tension builds as the line between reality and the game world blurs, with characters struggling to distinguish their true memories from those fabricated by "Circle." The narrative delves into the psychological toll of reliving traumatic experiences and the moral dilemmas of altering one's past. The climax reveals the full extent of Sensei's plans, culminating in a confrontation that forces Kaito and the other players to make difficult choices about their futures.

"Circle Sākuru" is characterized by its intricate plot, morally ambiguous characters, and exploration of existential themes. The story's structure, which alternates between the real world and the game's surreal landscapes, creates a sense of unease and disorientation, mirroring the characters' psychological struggles. The manga's focus on memory and identity resonates with broader questions about the nature of self and the impact of technology on human experience.