Aqua
I actually have not yet played Birth By Sleep yet but watched a playthrough of it when I was younger (didn't have a PSP as a kid). I just love her design and struggle to keep her friends from the grips of Xehanort. She strong!

Roxas
Roxas is a another big reason why KHII is one of my favourite games in the series. I loved his introduction as a confused individual without much of their memory, then slowly finding out their backstory and going against what they have been groomed into doing for the Organization

Oblivion & Oathkeeper
Some of the most recognizable Keyblades in the series and the Keyblades that Roxas use. Having played KHII before the first game, I felt it was a little more touching of a moment when recieving these Keyblades for the first time in the original Kingdom Hearts.

Twilight Town
It is my safe place ^-^ The theme here is one of the most comfortable songs from any video game. I used to spend hours riding around the town on the Skateboard when playing KHII on the Playstation 2 as a kid. And of course, being able to play as Roxas at the beginning is an added bonus. I was glad that we were able to re-visit in KHIII and do some odd-jobs there however I wish they had kept a few additional areas accessible like the tunnels and the train station. Here's to hoping that this world sticks around for future titles.

100 Acre Woods
I have always loved Winnie the Pooh as a kid, so the 100 Acre Wood was also one of my favourite worlds in Kingdom Hearts. It was a nice break from the more dramatic and combat-intense moments that the game can have. Being able to come here every couple of worlds to play a new minigame or talk to the characters living in the 100 Acre Woods was always exciting for me when playing through the series. Also hoping they keep this world around in KHIV.