- For the game created by Deep-Sea Prisoner, see Mogeko Castle.
- "Once, there was a lonely individual. Unable to bear his solitude, he made a kingdom solely for himself. He became the king of the land... A kingdom needs a castle for its king... So the king made one right in the center. This is that castle... but there was nothing inside the castle. It was just a world of nothingness. The king pondered. And he made seven Mogekos. Those were... the special Mogekos. They were put on each floor, to serve as that floor's guardian. Then the king made many more Mogekos, and the land became much busier. The king looked upon it, and was very satisfied. That was the genesis of Mogeko Castle."
– Defect Mogeko
Sometime in the past, King mogeko ordered Defect Mogeko, then known as Nega–Mogeko, to be executed for questioning his doctrine. Following Defect Mogeko being the first to be labelled as 'defective', after him every Mogeko who posed a danger to King mogeko's doctrine would be labelled "defective" and subsequently executed.
In Mogeko Castle
The castle serves to be the main obstruction between Yonaka and her brother, and the majority of the game is about Yonaka ascending the floors of the castle in order to reach the top, where she may return home from.
The castle´s walls are surrounded by a forest, and is somewhere near an 'abandoned' train station by the name of Mogeko Station, the station that the route of the Mysterious Train ends at. It resembles a stereotypical European castle, with various conical towers at its walls and a tall tower in the center of the castle, whose roof is shaped like a Mogeko head.
InteriorThe castle has seven floors, each with its own guardian, collectively known as the Special Mogekos. Some rooms aren't rooms at all, but in fact, "realms". Defect Mogeko mentions the castle having "infinite space" and always "expanding and extracting". Throughout the castle, absurd amounts of prosciutto and pornography can be found littered around rooms.
The guardian of the first floor is Somewhat Strange Mogeko.
The guardian of the second floor is Prosciutto Fairy. The floor contains a large amount of Mogeko larvae and is somewhat bright in comparison to the other floors from the castle.
The guardian of the third floor is Blood Spirit.
The third floor appears to house a prison of sorts, a prison that Defect Mogeko was imprisoned in, a prison that would later imprison Yonaka.
The third floor is the last floor accessible through stairs.
The guardian of the fourth floor was Hasu, until the day he was usurped from his position by Moge-ko. The Mogekos in this floor were described by Yonaka as being somewhat sad and downtrodden, likely due to the influence of the floor's new 'guardian' Moge-ko.
The guardian of the fifth floor is Moffuru.
The floor is inhabited by fluffy Mogeko-like creatures called Mofukos, who are in truth Mogekos that have been infected by lethal Blancfluff Mogeparasites, that are highly contagious parasites that affects normal Mogekos. Normal Mogekos do not inhabit the fifth floor nor are there any visitors to the floor aside from Special Mogekos, as the floor is used as a quarantine for those afflicted with the disease and awaiting execution by monster devouring.
Dead Mofuko souls fall from the sky in the fifth floor.
The guardian of the sixth floor is Mogecuckoo.
The sixth floor houses King mogeko's throne room. It also contains a gigantic library, and a room that resembles the first floor of the castle.
The guardian of the seventh floor was Nega-Mogeko prior his imprisonment. It was said by Somewhat Strange Mogeko (and, later, confirmed by Defect Mogeko) that it has a door that might allow Yonaka to return to the Human World.
- Mogeko Castle - The castle served as the main setting for the majority of the game.
- Four Obsolete Dream characters make cameo appearances within the castle: Kurotsuno appears on the second and fourth floors looking for her phone, and on the fifth with Hanten and Met once her phone has been found. Hanten and Met appear on the fourth, looking for Kurotsuno, then the fifth with Kurotsuno after she recovers her lost phone. Sullivan makes an indirect cameo, in the form of a letter addressed to Olivia.
- On the first floor, Yosafire and Wadanohara make a cameo in the form of miniature figurines on the top of Somewhat Strange Mogeko's shelf.