Spiral: The Bonds of Reasoning (スパイラル〜推理の絆, Supairaru: Suiri no Kizuna) is a fifteen-volume shōnen mystery manga series written by Kyou Shirodaira and illustrated by Eita Mizuno. It was published by Enix and then Square Enix in Monthly Shōnen Gangan from February 2000 to October 2005 and collected in 15 bound volumes. A prequel series by Shirodaira and Mizuno, called Spiral: Alive, was published in Gangan Wing and Monthly Shōnen Gangan from April 2004 to June 2008 and collected in five bound volumes.
The series was adapted as a twenty-five episode television anime series broadcast on TV Tokyo from October 1, 2002 until March 25, 2003. The anime is licensed in Region 1 by FUNimation, who released it on DVD and broadcast it on the FUNimation Channel programming block on CoLours TV in 2006. The series was also adapted as four light novels and a series of CD dramas.
In Spiral, Ayumu Narumi is a teenage boy who is accused of murdering Sayoko Shiratanagi. His sister-in-law is the one who is in control of the case, so she lets him go. Ayumu is determined to find the answer to the mystery, and, along with the head of the newspaper, Hiyono, figures it out. This sets off a series of events. He meets pianist Eyes Rutherford, Rio Takeuchi, Kosuke, Ryoko, and their so-called leader, Kanone. For some reason, they all seem to know his older brother, Kiyotaka, and they think that he can save them. Just who are the "Blade Children".
Two years ago, the famous detective Narumi Kiyotaka disappeared, leaving behind only the words, "I am pursuing the mystery of the Blade Children." Now, his younger brother Ayumu is accused of murdering a fellow student, and begins to discover people with connections to the Blade Children all around him. The Blade Children were born cursed, and Ayumu may be the only key to saving them, but first they want to test him, by trying to kill him with everything they've got. All the while, it seems that Kiyotaka is manipulating events for his own unknown purposes.