The story progresses through branching paths leading to multiple different endings, based on choices the player makes; the player only gets a full view of the story by playing through each route. Rather than starting over from the beginning several times to see different paths, the player can skip directly to the branching points using an in-game flow chart. During the investigation parts, the player character, as detective Kaname Date, uses his artificial intelligence unit Aiba's functions, such as X-ray vision and zooming, to further the investigation in the real world. During the somnium parts, Date uses a machine called the Psync Machine to enter the memories of suspects or key witnesses who do not want to share information with him, in the form of dreamscapes called "somnium", to find clues and extract the information by solving puzzles. The puzzles involve examining objects and choosing an action to perform with it, and solving mental locks – obstacles standing in the way of clues – allowing the player to sink deeper into the character's subconscious. There is a six-minute time limit before the dreamscape collapses, and as actions take time to perform, the player must be careful in deciding what to do. Within the somnium parts, Aiba takes on the form of a humanoid and acts as the player avatar. AI: The Somnium Files takes place in a technologically advanced near-future Tokyo, and follows Special Agent Kaname Date of the top-secret police department ABIS . ABIS investigates crimes through a process called "Psyncing," in which a Psyncer such as Date explores the Somnium, or dream world, of persons of interest in a case. Psyncing is a powerful process that can often retrieve clues the subject is only subconsciously aware of, but it is limited to a maximum of six minutes for the Psyncer and subject's safety. Date is assisted by an artificial intelligence housed in his cybernetic left eye named Aiba, who can communicate with Date via an artificial nerve, provide him with enhanced vision modes such as X-Ray and night vision, and hack various electronics. Date investigates Mizuki's dream to find out what she witnessed, and the plot diverges based on the player's choices in her Somnium. In the left branch of Mizuki's Somnium, Date finds evidence implicating Renju Okiura, Mizuki's father, before discovering his body with the left eye missing. Boss, the head of ABIS, reveals that she suspects the killer to be a copycat of the Cyclops Serial Killings, an unsolved case from six years prior in which the victims' right eyes were removed posthumously.