Ryôichi, a student, researches urban legends and is interested in how they are propagated. As several people suddenly and strangely lose their memories around him, he hears more and more about a mysterious monster, the Kiokuya, which is supposed to feed on people's memories. But does this Kiokuya really exist? And if so, what is its real purpose? Why would he try to erase the memories of those who come to see him?

The story is about a young wizard who visits the non-magical world to crack down on his company's unauthorized magic users, and a non-magical girl who end up working together to investigate a magic-related crime.