The Mobile Investigative Unit (known as "MIU") of the Tokyo Metropolitan Police Department attempts to solve cases within 24 hours. Detective Kazumi Shima is selected as a new member of MIU. He is intelligent, with excellent observation and communication skills. Yet, he does not trust other people. He is unable to find a partner in MIU and is ordered to partner with Police Officer Ai Ibuki, who works at a police substation. Ibuki applied for MIU, but he failed. He is in excellent physical condition, but he lacks knowledge and experience as a detective. Shima learns about Ibuki's background and he becomes more nervous. Finally, Shima has his first meeting with Ibuki.

MIU404 тривав 1 сезон. Нових епізодів не заплановано.