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.

Largo Lloyd, ousted director of the Beehive, saves the life of a Marauder--and, in return, demands to be taken to the leader of Reverse. Will the Letter Bees finally penetrate to the heart of the rebel organization? Meanwhile, with his hero Gauche returning home at last, things are looking up for Lag...until he discovers the shocking truth about Gauche!