THE DOUBLE-EDGED BLADEYuan wields a double-edged blade during the game and in the animation of Tales. He is very skillful with his weapon, and is able to summon it whenever he is ready to battle, (it is not normally exposed, so we see him summoning his weapon in his hand). Yuan's double-edged blade is different because instead of having two weapons, he combines the two blades together into one single weapon. Sometimes his weapon is referred to as "Swallow." There isn't a lot of information about Yuan's weapon itself, so I decided to get into detail about the weapon in real life.
The "double-edged blade," comes from the notion that if two sides of the same blade are sharp, it cuts both ways. The metaphor may have originated from the Arabic expression meaning "double-edged sword." In the Bible, the word of God is described as a being sharper than a double-edged sword. Norman swords normally had a broad, double-edged blade, and were about 76 cm (2 feet 6 inches) long. In Northern Africa, the double-edge sword had a leaf-shaped blade, and a handle which hollows away at the centre and thickens at each end. These swords are of various lengths, and were often paired with shields. In Chinese culture the double-edged sword, or jian, is considered a master's weapon or gentlemen's weapon, both from the considerable skill required to fight with this weapon and from the fact that commanders of armies favored the jian in order to move easily amongst the troops.
Often times, when you call someone a "double-edged sword," that means you have freedom of expression. I think that the weapon fits Yuan well because his character has a lot of built up emotion inside of him, and he needs to express it out through his fighting style. These swords are also characterized for people with discipline. I think because Yuan was a trained warrior, and has over 4,000 years of experience, he had a lot of discipline and learned the ability to wield a sword of this size and strength.