There are 6 endings in 999: Nine Hours, Nine Persons, Nine Doors. Five are bad endings, and only one is good. The ending you get is dependent on which numbered doors you pick during the game. There are four other decisions you make during the game which can affect the ending. These are explained in the “True Ending” section.
To get the True Ending, choose Doors 4, 7, and 1. There are four other decisions you must make in order to get this ending.
- Behind Door 4, in the 2nd Class Cabins, after finding the plate in the display case, Santa will offer you a bookmark with a four-leaf clover. You must accept it (if you don't, he'll insist once and you'll have a second chance).
- Behind Door 4, in the Kitchen, after finding the dry ice in the freezer, June will tell you and Santa about the sublimation point of CO2. You must respond with “It did strike Junpei as rather odd.”
- Behind Door 7, in the Operating Room, when Seven is about to remember something, Junpei asks “Do you…” and you must choose “… know about ice-9?”
- Behind Door 7, in the Operating Room, when talking to Clover, give her the four leaf clover bookmark you got from Santa.
If any of these specifications are not met, you will get the Axe Ending instead of the True Ending. Also, you must have already seen the Safe Ending, from a previous playthrough, and have saved it on the same file, in order to see the True Ending. If you have not, you will get the Coffin Ending instead.
To get the Coffin Ending, choose Doors 4, 7, and 1, the same as for the true ending. You also must make the same four decisions needed to see the True Ending. However, you will only get this ending if you have not seen the Safe Ending on the file you are currently playing.
The Coffin Ending is considered a “dummy” or “fake” ending, as it provides no new dialogue or information apart from the other endings. Instead, the game cuts off just before opening Door 9 in the True Ending, and says “To Be Continued…” If you get the True Ending, it will count as having gotten the Coffin Ending, and you not be missing any part of the story. So, this ending is not necessary to get.
To get the Safe Ending, choose Doors 5, 8 and 6. In the puzzle room beyond door 5 there is a safe in the closet of the bedroom. You must examine the safe after unlocking the door, but before leaving the room to get this ending. This is the bad ending that is required before you can see the True Ending.
To get the Knife Ending, choose Door 6 as your last door choice after choosing any Doors except 5, then 8, and then 6. This is one of the normal bad endings.
To get the Axe Ending, choose Door 1 as your last door choice. If you chose Doors 4 and 7, you must fail at least one of the decisions listed in the True Ending to see the Ax Ending. This is one of the normal bad endings.
To get the Sub Ending, choose Door 2 as your last door choice, or choose Door 3 as your second door choice, as it automatically leads to Door 2. This is one of the normal bad endings.