Reverse Hills is a dungeon in Shin Megami Tensei IV.
A building found underground beneath Roppongi Hills, it is a mirror of the building above, upside down. A path from Midtown, through a former Army shelter, leads to the building. B7F, which is also the entrance, is filled with rooms with gas-masked men working on people strapped to chairs. A gas masked man will hand over Card Key 2 to activate the elevator, believing the Samurai are "the next shift." B8F is devoted to child care; a gas-masked man with two kids will give Card Key 3 under the same assumption.
B9F is filled with demon walls, making it necessary to traverse through the entire hall to get to the room where Card Key 4 is at. Unlike the last two, the gas-masked man will attack with the Deceased Horde after being surprised when inserting a needle into his charge's head. After defeat, he will give the Samurai a brown-colored bottle and collapse; when frisking him, Walter will find the card key and confiscate it. The man himself, though, is severely brain-damaged, repeating in a childish voice the same Ashura-kai slogans the kids in the floor above were seen to chant. Another set of elevators leads to B51F.
B51F leads to a processing facility; most doors are locked, two through the use of a password. The Samurai discover what Red Pills are made of when an Ashura-kai employee takes the bottle and mentions it's brains, patiently explaining to Isabeau the horrifying process of the creation of Reds; people are abducted from the underground districts, conditioned as seedbeds and have their neurotransmitters harvested at regular intervals. After the scene, the floor will be filled with the sweet-smelling pink gas made by Yaso Magatsuhi and the group will be knocked out.
Revisiting the facility after siding with either Walter or Jonathan and collecting the Card Keys from the Master Samurai at Roppongi Hills allows the Samurai to challenge Yaso Magatsuhi as revenge for their earlier encounter. There is also an alignment-affecting question if rechecking on the children of B8F.
Reverse Hills is a human farm, its prisoners kept under inhumane conditions in filthy, bloodstained rooms also used as operating theaters. Most of the adults are used as seedbeds for Red production, and at least some of the children brainwashed by the Ashura-kai also meet this fate. Red production is at an ever-increasing pace, and the workers mention considering using the children in it as well, and referring to the women as "breeders." Many rooms have their prisoners brain-damaged due to overharvesting. Sanitary facilities are minimal.
Tayama, from witnesses in B8F, apparently sometimes visits the facility.