Tegami Bachi, Vol. 15

A New York Times best-selling sci-fi fantasy series with heart.
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.
Searching for the truth about Amberground, Lag heads home to the little town of Campbell. There, a woman named Sabrina Mary holds the secrets he seeks. But can he handle what he learns about his world, his government…and his own mother?