Moonlight Sword Style.
The most fluid and defence oriented sword style among the ones out there. It's more like collecting dense mana into your sword without any precision and then practising the normal moves on it.
After you have learnt to collect enough mana into the sword, you are asked to create a sword of mana without using an actual sword. This allows you to collect dense mana more easily while using the sword style.
The next step is to learn to move the dense mana in the direction where you want. At this point, you can even add your own skills into it. With the heavy mana filled sword, it's more like a heavy sharp rock coming at you.
While a sword will be coming at you, you will feel like you're going against a heavy rock.
But what makes it even more dangerous is its fluidity. That is, once you have mastered how to move the mana flow, you can move that heavy rock like sword anywhere you want.