Spiral: The Bonds of Reasoning, or Spiral: Suiri no Kizuna is a manga series written by Kyou Shirodaira and illustrated by Mizuno Eita. It was published by Square Enix between 2000 and 2005, with a prequel manga Spiral Alive running from 2004 to 2008. It was adapted into an anime by J.C.Staff before the manga was completed.
The story follows high-school detective Narumi Ayumu and his side-kick, the school journalist Yuizaki Hiyono as they investigate the Blade Children.
