The Sword of Flame is chapter 40th of Tsubasa Reservoir Chronicles.
The next morning, both Sakura and Fai have a hangover from the night before. Kurogane is taking Syaoran out into town to a sword shop. They are both there to buy new swords.
The shopkeeper verifies their status as kiji hunters, and immdiately hands the Kurogane a sword. The sword he receives is called Souhi (Blue Ice). The shopkeeper also identifies that Syaoran has never used a sword before.
He notices the fire burning in Syoaran's eyes. He calls his helper to bring out a sword. It is not easy to use, but he believes that Syaoran will be able to wield it. The name of this sword is Hien (Scarlet Flame).
Outside of the shop, Kurogane teaches Syaoran to only pull out the word when the time is right. A sword chooses its master.
It cuts off to where Syaoran and Kurogane return to Cat's Eye. Syaoran is covered in small scratches from Kurogane's training. All of the kiji have been acting strangely. They normally only attack hunters, but the have begun to target civilians. The new, human-like kiji may also have a link to Sakura's feather.
Souhi and Hien are from X