The story appears to be centered on the investigation of the Book of the Silver Cross, an ancient Belkan magical tome. Thoma Avenir, whilst traveling, discovers a girl named Lily Strosek trapped inside a construct. When rescuing her, she gives Thoma an amulet that gives him access to a new Device power. However, unbeknown to them, there is another with a similar Device causing massive damage and injury, leading to an investigation by the Time Space Administration Bureau.

(Source: Mangafox)