Zero Escape: The Nonary Games

Once you have completed all the branches of the timeline flow chart and obtained the Fire and Ice achievement, go back into the flow chart and go all the way to the bottom right corner. You'll find another hidden section below Phi's ending. Simply go through this novel section to unlock the achievement, no puzzle solving necessary!

I feel as though I need to make this as the first guide provided doesn't provide a full picture of what's needed as I had gotten the Fire and Ice achievement but did not have the extra bit below Phi's ending.

Players should make sure they have collected all Golden Files AND finish each room in Hard mode as I had a couple I switched in the middle of the puzzles and got an Easy finish resulting in me not having access to the Infirmary Another Time part. If you have finished some rooms in easy Mode however this is an easy fix as any levels finished in Easy you can simply finish in Hard as you already have the solution saved within your files.