Ink researcher Hirao at an Ink Company disappeared and received a mysterious threatening letter.Detective Tetsuko rushes to the Ink Company with Detective Yamanaka, but is shocked by the contents of the threatening letter. The condition for Hirao's release is to publish the details of the new ink on the company's website by midnight the next day.Kinu, at Ink Company's request, somehow manages to put together the patent documents in a short time and submits the application within the time limit.After that, a letter was sent stating that Hirao had been killed, and his body had been kneaded into ink. FuA suspense story unfolds with subordinate researchers, female detective Tetsuko, who is hostile towards Kinu, and a magazine reporter.