Ashinaka High School is known for its unique setting: the entire campus is built on an island. Yashiro Isana, aka Shiro, is having lunch with a cat on one of the school rooftops. After his lunch break, Shiro goes on an errand for his classmate Kukuri to prepare for their upcoming school festival, only to be chased by some intimidating-looking men.

Unable to find any traces of his own past, Shiro begins to believe that the person known as Yashiro Isana may not have existed. As Shiro and Kurou try to think of what to do next, SCEPTER 4, led by the Blue King Reishi Munakata, arrives to apprehend them.

Neko undoes the spell placed on Shiro to help him remember who he is. But other than a brief image of being thrown from an airship by a mysterious man, Shiro remains in the dark. Determined to regain his memories, Shiro takes the risk of contacting Reishi, the Blue King, who could lead them to the mystery man.

The Blue King, Reishi, accepts a proposal from Shiro to carry out an air mission to restrain the Silver King, Adolf K. Weismann. However, the mission is abruptly interrupted when the Silver King’s airship self-destructs. The following day, Reishi pays a visit to the Gold King, where he discovers the remains of the Silver King. In the meantime, an unknown force makes contact with the detained Mikoto.

The war between the Blue and Red clans intensifies as Mikoto and Reishi finally face off. With his memory restored, Shiro introduces himself to Kurou and Neko as Adolf K. Weissmann, the Silver King.