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. Letter and Letter Bee Gauche Suede is on his last delivery before a big promotion. In the outskirts of Yodaka, the darkest area of Amberground, Gauche is surprised to find that the package is a young boy named Lag Seeing. Lag had been traumatized by his mother's abduction and is due to be delivered to his aunt. In this remote area rife with Gaichuu, Lag and Gauche face a dangerous journey that inspires Lag to become a Letter Bee. -- VIZ Media

Lag now knows what he has to do to save Amberground: unite the five children born on the mysterious Day of the Flicker. And his latest delivery may lead him to vital information. But meanwhile Lag has to cope with his brash new partner, Chico, who insists that nothing will stand in her way to becoming Head Bee! -- VIZ Media

Lag and the other "Letter Bees" continue to fight against the metal insects known as the Gaichuu while the secrets of the world of Amberground come to light.

While Lag and his fellow Bees fight a desperate battle against the Gaichuu Cabernet, the dark secrets of Amberground come to light. What unspeakable things did Garrard, director of the Beehive, see in Amberground’s capital? And why has former director Largo Lloyd joined the rebel organization Reverse? The answers lie in the top-secret district called Kagerou... -- VIZ Media

What is the truth behind Amberground? As Lag and his friends descend to the center of their twilight world, they learn more than they ever dreamed possible. With civilization collapsing and the end of the world at hand, the time has come for Lag to lead the people of Amberground to hope and light at last. -- VIZ Media

Lag, now a Letter Bee rookie, meets Dr. Thunderland, Jr., a peculiar man who collects and catalogs the various Amberground species. When the doctor takes a particular interest in Steak, Lag and Niche have to hustle to keep him off the doctor's dissection table! The ensuing chaos pays off for Lag when the doctor reveals that Gauche—Lag's missing hero—paid the doctor a visit before he disappeared. -- VIZ Media

As Bees and ex-Bees alike gather in Yuusari, the rampage of the unstoppable Gaichuu Cabernet continues—and heart attacks only seem to make it more powerful. As it absorbs the attacks, Cabernet keeps morphing into stranger and more sinister forms. Meanwhile, a tragic accident triggers a different kind of transformation in Niche... -- VIZ Media