Letter Bee and Dingo is the 17th overall episode of Tegami Bachi, and is similar to the Pilot Episode, Light and Blue Night Fantasy.
Lag Seeing just finished a delivery and went back to the Bee Hive, to receive the next assignment that it's a personal delivery. The chief explain that it's a small package, to Elena Bran, who once worked as a bee, and a letter to Bart Bran, her younger brother in Yodaka.
The letter is from Largo Lloyd, the chief. Miss 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.
Lag visits a man's house. The man told Lag to be careful of the Dacquiose Cliff, because Elena Bran was killed by a gaichuu 10 years ago there. Lag decided to leave Darwin there because he's still weak; however, Darwin was awake and force himself to go with them when he heard about Elena Bran.
At the Dacquoise Cliff near Silencio, Niche finds no path because there's a landslide. Gaichuu Absinthe 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 pass 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.
During this delivery, Lag was to deliver also the matching pair that Lloyd found. Lag gave the small package (a pair of charms) and the letter to Bart Bran, Elena's brother. After that, Bart made a grave for Darwin beside Elena's grave and placed the charms on both of the graves of Elena and Darwin.