Magical Record Lyrical Nanoha Force
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)
