The Mizuhanome System is a cutting-edge technology that allows individuals to explore one of the most fascinating locations on the planet: the human mind. Detectives from the specialist police squad Kura can materialize a criminal's unconscious mind as a weird stream of ideas in a virtual environment by using so-called "cognition particles" left behind at a crime scene by the offender. Their mission is to investigate this psychological dimension known as a "id well" in order to identify the perpetrator. You can't just go into the id wells; you have to have murdered someone before. This is the case for former investigator Akihito Narihisago, who goes by the alias "Sakaido" inside the id wells. Tragically, he was once a respected member of the police force.