Land of Doppelgangers

 The is where doppelgangers live and flourish. The Land of Doppelgangers is an extremely large city in an alternate dimension. In that dimension, this place was known as Kaiyōgakure. The doppelgangers live in this land alone, and the only humans who come there are humans brave enough to learn the way of the doppelgangers. The Land of Doppelgangers isn't part of the human universe. It is part of Zen Jigen, following its systematic destruction. It can only be reached in two ways: The Choosing or Teleporting. "The Choosing" is a weekly event in which a doppelganger teleports a random 5 human beings to the Land of Doppelgangers to be tortured. If the target (or victim) can survive it, which is rare, the Doppelgangers will ask the target if they would like to learn the way of the Doppelgangers. If denied, the target will be returned to their home. If accepted, the target will stay for a time varying between 3 months and a year to train to become a Doppelganger Sage. The second option is Teleportation. This method is a highly risky maneuver, for doppelgangers hate trespassers. However, if the teleporter can survive their punishment from doppelgangers, which is torture (literally), then they will be invited to learn the way of the Doppelgangers.

City Hall: Home of the King of Doppelgangers
Destroyed homes and buildings are plentiful in the Land of Doppelgangers, but if a human is chose to become a Doppelganger Sage, then they will be taken to "City Hall". City Hall is a giant...City Hall. With many rooms there, the Royal Doppelgangers are only allowed to live there. Doppelganger Sages are allowed to stay with a Royal Doppelganger of their choosing, but the few Doppelganger Sages that exist claim that sleeping was the most dangerous thing there. Many crazed doppelgangers roam the halls at night. And since anyone can enter "City Hall", and doppelgangers are forbidden to kill one another, crazed doppelgangers often look for that rare Doppelganger Sage to kill, then eat. Actually, more or less eat, then kill, because doppelgangers prefer humans to still be alive when they eat them. The following day, the chosen Royal Doppelganger leads the Doppelganger Sage through a graveyard-like area to a tomb. This tomb is known as the Sage Training Facilities, which can only be accessed by a verified Doppelganger Sage-in-training and the King of Doppelgangers himself. The room looks like a tomb-meets-abandoned subway-area, and in the middle is a empty plaque where Doppelganger Sages-in-training are to sit a meditate. The markings on the walls inside tell the history of doppelgangers, and how they came to be. They also hold Natural Energy. Given voice commands through telepathic communication, the chosen Royal Doppelganger gives "advice" to aspiring sages as they meditate on the plaque to control their natural energy intakes and to utilize senjutsu. The Land of Doppelgangers actually takes in natural energy from dead human shinobi. When human shinobi die, the land itself gains a boost in natural energy. Doppelganger Sages-in-training are often in danger in the Land of Doppelgangers, having to dodge crazed doppelgangers left and right. Doppelgangers offer its human sages plants to eat, since that is all that's there. Besides from the alternative, which is eating a human being.