Reverse World is the 30th overall episode of Tegami Bachi
Numerous incidents of Reverse marauders attacking Letter Bees and stealing their letters is under investigation, with Largo Lloyd writing reports to the inspectors from the capital, Hazle Valentine and Caribs Garrard. The two of them soon arrive in Yuusari.
Moc Sullivan arrives with news of being ambushed and losing his letters in a ravine. When Lag offers to help retrieve the letters, Valentine and Garrard stop the Bees as they have no qualifications on dealing with Reverse, and they also suspect a leak within the Bee Hive. They soon leave to go investigate.
Lag, Niche, and Steak stow away on the inspectors' carriage. Soon after discovering the stowaways, Lag offers to help collect the letters when Garrard tells him he will reveal what he knows about Gauche Suede. After Lag and Niche are distracted by Garrard and Valentine respectively, Garrard uses a catalyzing agent that resonates with the hearts in the letters to attract a gaichuu.
After Lag and Niche destroy the gaichuu, Lag inadvertently finds a letter regarding the leader of Reverse, Lawrence. He reveals he is a failed man-made spirit created by an experiment sanctioned by the government and stirs up support from the populace for Ones Unable to Become Spirit.
Gauche (as Noir) is confirmed to be working for Reverse. Though disappointed, Lag remains firm in delivering letters for the people. Later, Lawrence listens to the results of the experiment to attract gaichuu from the inspectors, who are revealed to be working for Reverse. Lawrence decides the time has come for Reverse to make their next move and sends Noir and Roda to the north.