Lag Seeing, who was rescued at a young age by a national postal service worker known as a Letter Bee named Gauche Suede, idolized this Bee and finally met him again after he went missing. However he calls himself the Marauder Noir and steals the letter from Lag. Lag, injured, is saved by the Express Delivery Bee Jiggy Pepper and taken to the Bee Hive, but Lag's partner, his dingo Niche, doesn't take it very well...

Niche thinks she has failed at being Lag's dingo, so she runs away from home with her pet(?) Steak. Worried, Lag and Connor head out to search for Niche. However Niche, hungry and wandering aimlessly around town, sneaks into the bread and weapons shop Sinners and tries to finally cook Steak, but the Gobenis catch her in the act.

One day, while on a delivery to a certain mansion, Lag is asked by Ray Attlee the owner of the mansion, to search for the person who sent a picture-letter to her. Ray says that the pictures in the letters reminded her of her hometown, and gave her the will to continue to live on and fight her illness. Lag, after being called a "Letter Specialist" by Ray, decides not to rely on his shindan that allows him to see the heart contained in letters, and does his best to search for the sender. He discovers that the paints used to paint the letters have some connection to Ray's hometown, and then...

"Get away from here"... The boy Lugh works together with an old man he calls "Grandpa" in an imagery lighthouse built out in the wilderness, but he keeps hearing voices from somewhere. Around the same time, Jiggy Pepper is passing by the area on a delivery, and notices that a Gaichuu, Korona, has made a nest on top of the imagery lighthouse. Riding his "iron horse" up the imagery lighthouse, Jiggy Pepper's shindan Lapis Lazuli explodes!

Two inspectors from the capital, Akatsuki, come to the Bee Hive. Caribs Garrard and his dingo, Hazle Valentine. They came to investigate a string of letter robberies happening to the south. During one of them, Moc Sullivan is attacked, and the letters he was carrying fall into a ravine. Garrard suspects that there's someone on the inside for Reverse, since they know so much about the Letter Bee's routes and movements, so he forbids them from going to the south. However, one of the letters Moc was carrying was a letter from a sick girl that Lag dictated for her...

Sylvette receives a fan letter addressed to her from a girl named M. Croce, asking her to make a doll that looks like her to give to her brother who will be leaving his hometown to work in a coal mine shortly. The doll maker, Sylvette, hurries to make the doll, and after spending all night, heads out the next morning to deliver it. Lag is worried and goes with her, but the two of them are tired and end up falling asleep on the rhino carriage!

A person spotted Noir up in the northern reaches of Yodaka. Lag is ordered by the Bee-Hive Master Largo Lloyd to find out what Noir is up to, and he heads there with Niche and Steak. There he discovers a shell of what looks like a giant gaichuu, as well as a used cartridge which Noir left behind. Lag shoots his own shindan into the cartridge!

Lag visits the town of Blue Notes Blues, steeped in the legend of the Maka, the mysterious creature deeply connected to Niche. The people in town witnessed someone like Noir heading into a cave, however the Mayor, Khari Tonov, tells them that cave is where the Maka lives and is dangerous, and entry is forbidden no matter who it may be. But despite this, at Niche's suggestion, Lag heads toward the cave wanting to find out more about what Noir was up to.

200 years ago, Niche and her twin sister were shunned as cursed, and were eventually disposed of. Thrown into a river, with the most precious thing in the world, her sister, split apart from her, she matured all on her own, and has lived together with the Maka ever since. When Niche finally encounters her, she has no recollection of what happened, and instead protects Lag, a "human." Shocked by seeing her sister in such a state, she tries to kill both her sister and the other people. Lag tries to stop her, and shoots a shindan into her with his feelings...

With the wounded Niche left in the "Garden of Spirits" which the Maka protects, Lag runs into Zazie on his way back to the Bee Hive, and they stop by the town of Lament where Connor is. There, the two of them are surprised to find Connor collapsed, but it was because he'd eaten too many cookies from a nun named Sunny. Lag witnesses Roda, Noir's dingo, picking up a delivery of letters at the Abbey where Sunny lives, so he goes undercover and infiltrates the Abbey to find out if it is a Reverse base.