Tegami Bachi: Letter Bee

A Letter Bee is a government employee working for the national postal service, responsible for delivering written messages and packages to even the most remote locations. They must traverse Amberground, a dangerous land blanketed in constant twilight. Letter Bees are highly respected for risking their lives to connect people across great distances.

The monsters that roam the land of Amberground are known as Gaichuu. These armored beasts are attracted to the "heart" (fragments of human emotion) contained within the letters the Bees carry. Letter Bees must use a special weapon called a Shindan, which fires a piece of their own heart as ammunition, to defeat them.

Gauche Suede is a highly skilled and respected Letter Bee who serves as the main inspiration for the protagonist, Lag Seeing. However, Gauche eventually goes missing during his deliveries, leading Lag to become a Letter Bee himself to find him. Lag later discovers that Gauche has lost his heart and joined a rebel organization called Reverse.

The series is set in a dark, steampunk-inspired land called Amberground. The land is divided into three distinct regions based on wealth and social class, and it is perpetually shrouded in twilight because its artificial sun only illuminates the capital city. The treacherous environment makes the Letter Bees' jobs incredibly perilous.