Rats in the House of the Dead

The Rats in the House of the Dead (死の家の鼠,) is an underground organization led by Fyodor Dostoevsky.

Logo
The logo of the organization consists of a cartoon-like design of a rat's head, with big hollow eyes and an enormous grin.

Influence
Like The Guild, it affiliates with Order of the Clock Tower in order to obtain the Book.

According to Dazai, their goal is to get the "The Book" however, in order to get the book, they need to exterminate the city of Yokohama, but they don’t have the strength of the Guild to incinerate the whole city. Therefore, they use killings to defeat the Armed Detective Agency and Port Mafia.

Atsushi's Bounty Approach
Rats in the House of the Dead takes part on the bounty plan on capturing Atsushi in order to obtain the book.

The Incineration of Yokohama
During the Guild’s second part operation - Operation "Moby Dick Drop" - to obtain the book and its foreseen descent to the land, Fyodor Dostoevsky override the control system of Moby Dick to successfully execute their plan in wiping out the Armed Detective Agency and Port Mafia. However, this plan failed when a member of the agency manages to crash the Moby Dick to the sea.

With the plan being a failure, their plan to obtain the book still stands. They have stirred unrest with the Guild and seized 40% of their assets, damaged Yokohama and weakened their foes. Fyodor eventually scouts Nathaniel Hawthorne with the latter lending the group a hand for a while for the purpose of helping Margaret Mitchell come out of her coma.

Fyodor's capture by Ace
After the Guild war, Fyodor lets himself be captured by the Port Mafia, specifically by a man named Ace, one of the five mafia executives. While the executives and the leader discuss his fate, he is detained in an underground prison. Fyodor is then transferred under Ace's watch. Fyodor successfully outsmarts Ace, frees himself from Ace's capture and manages to steal the list of Port Mafia's ability users, eventually stating their next objectives, the annihilation of the Port Mafia and then, the Armed Detective Agency.

Cannibalistic Mutual Destruction Operation
The Rats launched their next attack by infecting the leaders of agency and mafia by the cannibalism virus that almost plunges the two organizations into a blood battle with their respective leaders' lives on the line. The plan ended with Fyodor's arrest and the rewarding of the Agency by the government with the Shikyuu Award that acknowledges their contributions to Yokohama.

Mushitaro's Arrest
During the cannibalistic mutual destruction plan, it was revealed that the Rats has a member responsible for suppressing and erasing evidence - who framed Doppo Kunikida of child murder during their pursuit of Alexander Pushkin. The member reveals to be Mushitaro Oguri The agency's pursuit of Mushitaro leads to him being revealed as the killer behind an author's death and the agency figuring out Mushitaro's original plan of appearing dead in order for him to run away. Eventually, Mushitaro agrees to turns himself in after hearing the agency detective reveal the truth behind the author's death and realizing that he cannot let his friend's death be in vain.

Trivia

 * The Rats used music as codes to communicate with each other during their cannibalistic mutual destruction operation.
 * Nutcracker Suite's “Waltz of the Flowers” translates into "Make it out there alone".
 * Bach’s “St. Matthew Passion” translates into "Now’s the time".