There is something called "Damage Shift' Where if you press the guard button on right time of enemy's attack, you don't get hit and this consumes 0 MP. This is basically the Just-Guard Tabata talked about,
There is also something more but it's spoiler so I won't mention it.
We already saw this in one of the gameplay videos, but I can't point to it myself.
It doesn't even have to be in the Phantom Sword state, either I think.