Their names and swords are intertwined.
Xiao xingchen sword name. He hadnt even meant to meet him until now but Xiao Xingchen just like in his past life has a heroic streak and the accompanying lack of self-preservation. On Xiao Xingchens 17th birthday Song Lan tells him the truth.
The novel states that when Xiao Xingchen stabbed Song Lan unaware that he just fatally wounded his closest friend Song Lan did not make any move or sound because he didnt want Xiao Xingchen to realize what he just did since the truth would break him. Wei Wuxian helped Xiao Xingchen up hoping to find a place for him to lay down but couldnt find a suitable location. He wields the Shuanghua Chinese.
Xiao Xingchen stood on top of the mountain in the night. Xiao Xingchen and Song Lan are called 道长 daozhang because 1 they are 道士 daoshi and 2 its the respectful way to speak to a practitioner of the Dao just as 兄长 xiongzhang is the respectful way to address ones elder brother.
If you didnt already know they came as a set the epithets the cultivation world bestowed upon them wouldve told you that. The black edge of his robes danced against the snow white fabric glowing in the light of their swords.
It is later used by Xue Yang to impersonate Xiao Xingchen. But back to Shuanghua first of all both its name and appearance are devastatingly beautiful much like its wielder.
Still clinging tightly to. Shuanghua Xiao Xingchen whispered reached a hand to the hilt of his sword a finger resting lightly on the pommel. Gentle yet strong in his convictions Xiao Xingchen left his teacher the Immortal Baoshan Sanren to wonder the cultivation world.