The Fallen Iron

Yin and Yang are the most fundamental properties of the world, which is like the two sides of a coin. A good example is our universe. At the very beginning of this universe, the heavy and dark matters, which represented Yin, sunk and formed the land, while the light and clean matters, which represented Yang, rose and formed the sky. And it is exactly the same way with the Seitenteil Sword. As you can see, the remaining part of the sword is Yin, so we will need some Yang metal in order to repair it.