Zero Escape: The Nonary Games (UP)

To open the second lock, first you need to find the researchers journal by going through the Yellow Door choosing Ally in the first AB Game and then choosing the Red Door. After completing the escape room you'll find the researcher's journal in the safe and need to have Phi translate it during the following Novel section.

To find the second lock once you have the journal, you need to go through the Yellow Door, choose Ally in the first AB Game and then go through the Blue Door, finally you need to choose Ally at the second AB Game. As long as you got the journal before this, you should automatically unlock this achievement after a few more conversations.