Letter Bee and Dingo (chapter) is the special chapter of Tegami Bachi Manga
Lag Seeing just finished a delivery and went back to the Bee Hive to receive the next assignment that it's a personal delivery. Largo Lloyd explains that it's a small package to Elena Bran, who once worked as a bee, and a letter as well to Bart Bran, her younger brother in Yodaka.
The letter is from Largo Lloyd, the chief. Aria tells Lag Seeing that there will be a guide around Lake Olympia known as Darwin. Lag Seeing asks for Darwin everywhere, and all he manages to find out is that Darwin is a veteran. Lag Seeing and others follow Darwin to Bifrost.
Niche quickly becomes angry during the journey, arguing with Lag that she is his Dingo, and wonders why Darwin is acting like his Dingo. Lag calms her down and they proceed forward. Soon, when Miss Aria and the chief are in a conversation, Miss Aria asks the chief why he hid from Lag that Darwin was Elena Bran's Dingo when she's on duty and the real package to Elena is Darwin.
At the Dacquoise Cliff near Silencio, Niche finds no path because there's a landslide. Gaichuu Absynt attacks, and when Lag shoots a shindan, he sees Darwin's heart. Elena had gone for a delivery and left Darwin at the Olympia Lake because he was hurt, and called him to wait for her but she died. Largo Lloyd (when the chief was young and still only a Letter Bee) told Darwin not to wait, but Darwin didn't care about his word and kept on waiting.
After Lag followed Darwin through the cave to Silencio, he saw Elena's grave. Darwin was seen laying beside Elena's grave, and then died soon after. Lag saw Elena's heart: Largo Lloyd and Elena were good friends before she died, and she asked about his charm because it's nice. He tell her that it's a rare item and that there is another matching pair.