Mystery writer Kosaku Asahina scores yet another scoop in a case that occurred in the streets. He even personally conducts investigations and frequently makes these cases the basis for his own novels. It maybe because his late father was a scholar that he is cool, but brims with curiosity and action. One day, Kosaku is facing the computer in his living room and writing a new novel. The novel is based on the baffling case of a female who fell to her death in Setagaya in the past. Kosaku had personally conducted interviews and inspected the scene of her death, but still cannot get to the truth. Then a letter addressed to his father Konosuke who died more than 20 years ago, is delivered to Kosaku. The name of the sender is the female whose mysterious death from a fall, is the subject of Kosaku’s new novel.