This achievement is earned during Act 1, when your objective is to "Help AJ Make Friends", back at the school courtyard. You'll have to speak to every available person/group before seeing Marlon. There should be 5 optional conversations to have, and having all of them will unlock this. The following missable achievement can be seen in the video below at 2:14
If this is missed, players will need to restart the episode from the beginning. It is advised that you back out to the main menu, and copy your saves manually every once in a while just in case to allow for an easier mop-up.