User blog comment:Disfigure/This was only shown in the Anime about Guren Ichinose/@comment-84.73.60.64-20160131005307/@comment-24726063-20160207132027

I'm pretty sure it has to do with the holder of the weapon.

The Ichinose familiy (at least Guren) had incantations on the scabbard of his sword, which when he activates them, make his sword crimson red glowing. So it could be that he used this magic on his sword in the fight. Still you could be right or maybe it only will happen in the anime and has no meaning to it, but my guess it is about this magic curse.