The only way to open the door was if the players who authenticated had their numbered bracelets added up to 26, or 8 when it comes to digital roots. It could also be seen as a "9" in base-10 or "q" in base-27.
In the case of the game, 2 + 4 + 5 + 7 + 8 = 26 = 2 + 6 = 8.
Behind Door q
The DEAD is right behind the door. A large, spiral staircase can be seen up ahead, behind a silver door. The staircase leads up to the top deck of the ship on the Gigantic. In Building Q's case, it's the exit and leads to the roof.
- In the Japanese version of the game, the explanation for why the door opened with only the digital root of 8 was that the letter "q" and 9 make the exact same sound in Japanese (kyu).
- In the First Nonary Game, this door actually was a 9. This is seen in the flashback of the game and was the only thing that was changed for the Second Nonary Game. Snake also states this door opened for a digital root of 9 during the First Nonary Game.
- Ace, in some of the bad endings where he is able to freely escape, would likely have trouble working through Door q and may have had to use trial and error.
- In the Axe Ending, is is implied Clover does not escape past Door q. It is possible she is incinerated to death in this ending because she lacks the bracelets.
- In the Second Nonary Game, Aoi and Akane quietly exit Building Q without the remaining other players. If they did exit it with them, they presumably still wouldn't be able to open Door q because the digital root would be 9 (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 45 = 4 + 5 = 9). Even with the true values (1 + 2 + 9 + 4 + 5 + 0 + 7 + 8 + 9), their digital root would still be 9 and it still wouldn't open. It can be assumed that either Akane or Aoi had a backup plan, or all of the players could escape when the door opened after only a select few opened it. At this point, Aoi/Akane would probably reveal that there are no bombs in their bodies (sans Teruaki Kubota and Nagisa Nijisaki), and that there's no penalty for entering Door q.
- The inclusion of the second 2 bracelet worn by Nijisaki and the O bracelet worn by Kagechika Musashidou, however, does result in a digital root of 8. (1 + 2 + 9 + 4 + 5 + 0 + 7 + 8 + 9 + 2 + 6 = 53 = 5 + 3 = 8). That said, it is likely the 3 - 5 bracelet rule still applies even to Door q as Junpei still only scans five bracelets in order to get through.
- In Virtue's Last Reward, the final puzzle room is a highly complex room known as Q, its name referring to the quantum mechanics (namely Schrödinger's Cat) that are used in that room. Noticing its name, Junpei says "Really? Now someone's just being a smartass."