Rei, Reo, Rekka, Jabi, Kaoru, and Gonza arrive to the Amber Rock Valley dig site where Gyanon was originally buried to save Kouga from Sigma realizing Idea. Reo and Rei takes on an army of G?ry?jin and receives unexpected assistance of Wataru. Meanwhile, Jabi and Rekka escorts Kaoru into Idea's core to find Gyanon and free Kouga. However, Sigma's minion Gigi has followed them. The two priestesses battle and eventually defeat Sigma's follower while Kaoru reaches Kouga. Kaoru manages to liberate Kouga by reminding him of who he is with the last page of the her father's book, Golden Knight and the Black Flame. With Gigi destroyed and Kouga freed, the group manages to escape Idea. Moments later, Sigma transports the incomplete Idea into the True Demon World to complete his creation. Wataru, Rei, and Reo follow by riding the core of Idea. The trio witnesses Idea's completion, as well as a display of its power as it destroys an entire horde of Horrors. After telling Jabi and Rekka to take Kaoru to safety, Kouga enters the True Demon World to join in the pursuit but must cut through his blocked path. The other three Makai Knights find Sigma within Idea's helm and are overwhelmed by him before he attempts to retrieve more power from Gyanon's corpse to replenish his strength. To everyone's surprise, Gyanon awakens and devours Sigma before revealing its true form. When Gyanon begins assimilating Idea, the Makai Knights retreat and watch as the greatest anti-Horror weapon ever made becomes an extension of Gyanon's body.