Very nice!
This scene plays very well.
Those characters are fascinating to look at.
There are two minor things I'd note for enhancement.
1. The characters hair seems to jump in place.
2. As the sword transforms in the fire a blending of the images together would sell the transformation.
This is a tough one to describe so if I get some time tonight I'll try to demonstrate what I mean.
Alternately, moving the shots where the camera pans across the characters in front of the shot where the boy in the flames is revealed might flow better and address the static transformation shot I mention above. I assume the next shot may have the boy step out of the flames?