Building Q was a building related to the Nonary Game, being used in both the First and Second games. It was supposed to be a complete copy of the Gigantic, but it was located in the middle of the Nevada Desert.
Despite being a building in the middle of the desert, the interior of Building Q looks exactly like the Gigantic; thanks to a variety of features inside the building, most prominently rushing water that flows into it and sound effects that resemble the creak of a ship, a person placed inside Building Q would believe that they were on a ship in the ocean had they not known its true nature.
It is still unknown why the building is named "Building Q", but Q is a frequently recurring letter in the series.
Building Q's interior was built as a copy of the Gigantic's. Due to this, the puzzles were exactly the same. Just like the Gigantic, Building Q had multiple decks connected by a Central Staircase.
D Deck held the 3rd Class Cabin, and was flooded at the beginning of the Nonary Game.
First Nonary Game
Building Q was used by Cradle Pharmaceutical and Free the Soul for the First Nonary Game to put the kids in Group Q, who excelled at transmitting through the morphogenetic field, to transmit the answers to the puzzles to the kids in the Gigantic. Clover Field and Ennea Kashiwabara were in Building Q.
Due to a mix up regarding Akane Kurashiki, Akane was sent to the Gigantic instead of Building Q. To fill in Akane's missing role, there were two sisters in Building Q.
Nine Hours, Nine Persons, Nine Doors
Building Q was later used by Crash Keys for the Second Nonary Game, as the Gigantic had been sunk in the previous Nonary Game. Its presence was only made known after the players of the game had escaped, as they had previously assumed they were on a ship because D Deck had been flooded.
After the survivors escaped from the building, they left in an SUV to track down their captors. On their journey, the group ran into Alice, who was attempting to get to Building Q after being tipped that the Myrmidons were stationed there. Alice joined the group in their pursuit but failed in reaching their detainers.