This is story related and can't be missed. You will get to a point in the story in which you have to go through the Royal Ruins. You will be asked questions at the end of each area and at the end of the fourth area, after the question, you will proceed up some stairs and this trophy will unlock.
If you get an answer wrong then you are sent back to the start of the area and have to fight back to try again. There is always a shortcut button just before the question area. The correct answers to the questions are:
*** Spoiler - click to reveal ***The first question about a king giving a ring to someone - He was unjust
The second question about a villager following you that may be a monster - Don't eliminate her
The third question about someone amongst you not being human - Aeterna
The fourth question about a Kingdom needing a king - No