Opened with the telling about the disappearance of Kiyotaka (Ayumu’s older brother) and the event that Ayumu turned into a suspect for attempt to kill Sayoko, who fell from a high building. Sayoko did not die though since she was fortunately cushioned by a truck, which happened to park there on that day. With the momentum reduced, she survived. However, all her memory was lost. Narumi, who was unfortunately the only man in the spot that Sayoko fell from, suddenly turned into a suspect. With this, Ayumu was forced to involve in this event and to get himself out from being a suspect. From the evidences in the scene which are glasses, loosened fence in the spot that Sayoko fell down as well as the behaviour of the real culprit, Ayumu correctly tore his mask off and showed the trick that person used. This forced the murderer to flee away. However, the key to other episodes of Spiral was the word, “Blade Children”, that the guy mentioned when all his guilt was testified by Narumi.

The stories about the “Blade Children” were what Kiyotaka was following before his mysterious disappearance. Therefore, it was the key toward the search for lost Kiyotaka and the identity of the group of Blade Children. The following cases were all related to Blade children. Ayumu was involved in most of them and he solved various clues. Out of these, there are various situations that Hiyono became greatly involved and, without her, Narumi would not be able to get enough information. The games of challenges and the gamble of lives had begun, gradually unfolding the real intention of the Blade Children.