Is the True wind rune Incarnate using a True Earth Rune spell, Sasarai himself doesn't have access to?
It seems to be a variation of Canopy Defense, except it reflects instead of repels(the reflection doubles as a repel anyway).
All I know is if you use an attack spell on it, you get the huge True Earth Rune image and then everything is cast back. IMO this is the worst part about this boss, and a bit unfair.
Edit: Can a mod please move this to the Suikoden III section.. I don't know what I was thinking when I made this in the Suikoden V section..