As mentioned by several different characters in the series, is absolutely massive. Easily capable of housing a large city inside itself, entrepreneurs of the magic user world gather there in hopes of starting up a business and selling goods to the powerful En family.
It consist in a humongous palace with hundreds of buildings covering the outside of the place, inside, hundreds of smalls houses, cafes, parks, storage buildings, and the residence of every En Family member, from the top officers to the goons.
Many festivities are held inside the state, The Blue Night Festival is one of them, a moment of the year when Magic Users come to the mansion to apply for a partnership with some of the family members, engaging in a three day free-for all blood bath which ultimately ends in they partnership of horribly murder.
Most of the everyday of the En Family members takes place there, thanks to the vast amount of rooms and places, many stories can be told and is the main place where "The Blue Night Festival" story arc takes place.
It is eventually taken over by the Cross Eyes gang and ransacked following En's death, with many of En's belongings being vandalized or destroyed. Upon his revival, En expresses dismay over the decrepit state of his manor and vows to make the Cross Eyes pay.