A prequel (with the same character designs as the anime) that takes place six years before "Guardian of the Spirit", this is the origin story for Jin, one of the Imperial Hunters. Prepare to see a fairly normal, slightly-spoiled tween be transformed into a small emotionally-unstable murderer following repeated tragedy. Contains: court intrigue, child abuse, young romance, tsundere, bullying, attempted murder, actual murder, and some seriously messed-up parenting. The story also features Hyoku, another Hunter, who is the same age as Jin; the other Hunters and the Master Star Reader appear as well, and the Emperor and his sons have very small cameos.

From the book jacket:
Another “Guardian of the Spirit” world!! Lost boy Taiga suddenly becomes the Hunter Jin. The future Hunter Hyoku, Suyou trains as much as possible. Together they will confront a fiery conspiracy in the palace! The secret past of the “Guardian of the Spirit” character, Jin the Hunter. Completely original story.