You need four items to unlock this trophy
First you'll need 2 optonal aeons.
Yojimbo
Anima
Then you'll need the blossom crown and Flower Scepter. To get the Blossom Crown capture one of every monster in the Gagazet set The full list is as follows
BanderSnatch
Grat
Bashura
Grenade
Splasher
Achelous
Maelspike
Ahriman
Grendel
Mandragora
Behemoth
Dark Flan
Note: Ahriman Grendel Mandragora Behemoth and Dark flan appear on the Zanarkand Ruins Road. they may not actually appear in Gagazet. Different versions of enemies appear in Mt. Gagazet, Gagazet, and Zanarkand Ruins Road.
Once you capture all those enemies return to the monster arena and he will award you with the Blossom Crown.
Finally for the flower crown you'll need to get a Chocobo License, as you can learn how to do here:
Then after getting the license request a chocobo on the calm lands and ride him to the south east corner of the calm land map. where you first entered the calm lands. Once you get there you'll see a chocobo feather to the left. If you go there your chocobo will fly down to a another platform with and exit. taking that exit leads you to the Remiem Temple. There you'll meet Belgemine if you've fought her every chance you've gotten ( Mi'hen high road, moonflow, and calm lands). You can now fight every one of her aeons, the only one you need to fight however is Bahamut. When you win against Bahamut, you'll get the flower scepter.
Up to this point these steps can be done in any order. once you have all the aeons and the flower scepter and blossom crown, you can go to the door behind Belgemine in the Remiem Temple and open the door, earning the final Aeon, earning this trophy as well as