Dual wielders are truly rare within the confines of his Four Heavens, especially for sword wielders. Using two swords makes it extremely hard to defend, and an extreme level of flexibility is required to wield two different weapons accurately. One misstep and everything comes falling down.
Within the world of Quadralia or the cosmos, where you could lose your life on any unforeseen day, wielding a weapon that might hinder you in the middle of a battle is not a good choice. In truth, Xiao never thought he would dual-wield. But in the past, he perceived one thing about his body.
His skeleton was extremely flexible, allowing him to perform maneuvers that would normally be impossible for others. In his previous life, an expert had examined his body and determined that he had a special skeletal structure that made his body much more flexible than anyone else's.