Originally a psychiatrist, Rokushiki was a genius who aimed to master all aspects of medical knowledge and technique. Rokushiki was arrested by Tokisaka, with whom he shares a complex history, during the resolution of the 'Girl of the Shell' case involving Mamiya Shinzou. He has been detained for over two years in a substitute prison operated by the Tokyo Metropolitan Police Department. He has intricate connections not just with Tokisaka but also with Masaki.