Amberground is locked in darkness. A man-made star casts only a dim light over the land. The pitch-black wilderness is infested with Gaichuu--colossal insects with metal exoskeletons. The Gaichuu make travel between the cities of Amberground extremely dangerous. But thankfully the Letter Bees, a brave corps of messengers, risk their lives in order to keep the hearts of Amberground connected.

Lag arrives at the town of Lament determined to save the heart of his fallen hero, Gauche Suede. Gauche's rebel organization, Reverse, may be hiding out in the town's convent. To get in, Lag will have to use his wits, and he has no idea what-or who-awaits him there. Will this be Lag's chance to fire his Letter Bullet and restore Gauche's memories...or the end of his career as a Letter Bee?