User blog comment:ChishioKunrin/My take on the Volume 3 Trailer/@comment-26397825-20151026021509

That girl with red hair and the curvy blade is wielding a Flamberge - or flame blade as it is translated into english. They're actually useful for disarming your oponents, as the vibrations from hitting a flamberge are different from the vibrations of hitting a normal sword, and is not something most people have experience with. This in turn makes it more likely for their grip to falter and the user of the flamberge can then disarm the opponent easier.

Not that I expect RT to actually utilise this properly. But the design is there.