Now describing a trailer can be difficult to do and can be hard to understand so I'm going to try to be as descriptive and detailed as possible.
Music slowly fades in as picture also fades in. You see a barren field at night. The camera is at ground level. The camera slowly pans to the left. As it pans you see bodies on the ground. The bodies move slightly to let you know that they're still alive.
The camera then cuts to a shot at a heart shaped moon then slowly swings around to give us a bird's eye view of the field on the bodies. You then see someone walking through body littered field. The camera cuts to a shot behind the person's head but still allowing you to see where the person is looking. The person is wearing a mask that their head but you can tell that the person is a girl.
The music that has been playing fades out. She stops. She looks to her left. The camera is zoomed in on her head as she's looking left. Suddenly there's a man right in her face. In, slow motion, you see his hand slowly reach her face then blasts her away while the speed returns to normal. At the moment she gets hit, the music comes back will full intensity. The camera then cuts behind her. She recovers from the blast quickly as she does a backflip to land on her feet.
The man walks slowly towards her. She casts a some kind of water spell that attacks the man at a high speed. But the casts a reflectga spell that makes short work them as he continues to walk closer.
The girl then casts a huge Firaga spell the sweeps the land. The man leaps in to the air avoiding the spell. The camera then cuts to behind the man as he looks down at the girl casting the spell as the fire spreads far and wide. He then slams back into the ground casting some kind of earth spell that causes the ground beneath the girl to rise out the ground and launches her into the air. The camera cuts to a low angle shot showing flying through the air eclisping the heart shaped moon.
He then appears behind her. She gasps as he casts a very powerful Thunderga spell against her body. Her body then falls almost lifelessly on to the ground. The music now slows and is more quiet. The man lands on his feet and starts to walk toward her again. As she struggles to stand, you can see from her point of view, that the man has stopped walking. She looks up and sees him take a step back. The music starts to build again.
You then see a hand on the shoulder of the girl. She looks up and there is a man who's wearing the same kind of mask she is. You see a shot of the girl's face as her mask falls off because the damage done. You still can't see her face completely but you can make out her red hair and a smile.
The music is building and building. The camera then cuts the back of the head of the new man as he turns his head toward the first man.
The camera slowly pans down the back of his body towards his hand. The music is intense and still building. Once the camera focuses on his hand, the music stops. You then suddenly see a silver kingdom key blade materialize in his hand.
The camera cuts to black as the music starts playing and intense orchestrated version of Simple and Clean.
You then see the words "Kingdom Hearts III" fade on to the screen.
I hope this wasn't too confusing and I hope you enjoyed it! :)
Until next time, my friends!