A woman in glasses with a spooky atmosphere and a little modest, is the client of today. She wants to find out the identity of a man who she sees running every morning during her commuting time. The woman was fascinated by the exceptionally fast running man, who she saw one day while riding the bus. According to the woman, the runner goes back, and forth to and from the same place every day. He finishes running in less than 2 hours the same distance, that is the same length as a full marathon. Muraki debates whetherto believe such a delusion story from the woman. During the investigation he reveals the hidden secrets the man holds to his running speed.