A young boy with silver hair is shocked and frightened when a group of mysterious men burst into his home and kidnap his mother. That same day, a handsome young mail man with similar silver hair introduces himself as Gauche Suede and informs the boy, named Lag Seeing, that he is a package to be delivered to his aunt by the Letter Bee mailing system. Lag reluctantly follows Gauche at first, but when Gauche tells Lag why the mailing system exists, Lag is strongly moved and begins to appreciate Gauche's efforts. When the time comes to stay with his aunt, Lag is saddened that Gauche must leave him. However, Lag begins to realize that this isn't goodbye forever, because he learns that he can apply to become a Letter Bee himself. When Lag passes for entry into the job role of a Bee, a rigorous path laden with monsters lies before him on his way to finding Gauche again.