This trophy is titled "
The Isle of Seiren" and it requires you to complete Chapter 1 of the game. It is a story trophy, thus, unmissable.
A brief rundown of Chapter 1:
*** Spoiler - click to reveal ***In Chapter 1, you will meet Laxia as you explore. Eventually, you will come to a large area with no beasts where Laxia sees someone.
Proceed into the nearby caves and progress through them. You will come to a large circular room and fight a boss named Byfteriza. The boss is straight forward, just constantly attack and use skills. Nothing special to this boss. Exit the cave at the other end to find the Captain.
You will be returned to the area with no beasts where Laxia first spotted the Captain. Exit the area to the right of the caves and then take the left path to continue exploring. You will eventually come across another crystal, usually signifying an upcoming boss fight, and beyond it is where you meet Sahan and then fight Avalodragil. The key to this fight is wait for the beast to bite, dodge, then attack its head. It is heavily armored, but its head is weak after it attacks.
Once defeated, return to camp. Several cut scenes occur and Chapter 1 will end. However, the trophy will not yet unlock. Laxia will wake Adol up in the morning with an offer of changing into a new set of clothing. Change or don't change, after the outfit tutorial, then the trophy unlocks.