Tessaiga is Inuyasha's sword given to him by his father when he died, originally forged from his own fang to protect his human wife (Inuyasha's mother). The sword as well as its sheith also have the power to produce a barrier that protects Inuyasha and his human companions at several points in the story. This barrier also keeps away full demons from wielding Tessaiga, therefore Sesshomaru, Inuyasha's brother, is unable to possess it. In its dormant form, the sword appears rusty and dull, however, after Inuyasha infuses his demon power into it, it transforms into a giant fang. Inuyasha was not able to transform the sword until he swore to protect Kagome and he continues to use it to protect his friends, which was Inuyasha's father's intended purpose for the sword. The sword itself holds many powers and capabilities, such as the Wind Scar and Backlash Wave (those are the moves in English) as well as the ability to absord demonic energy to create new moves such as Adamant Barrage, Dragon-Scaled Tessaiga, and Meido Zangetsuha. The sword also has the ability to keep Inuyasha's demon blood in check so that when his life is in danger, he does not turn into a murderous full demon. However, if Tessaiga is not in Inuyasha's possession in battle and he is close to death, his demon blood takes over until Tessaiga is in his hands again. Over the course of the story, Inuyasha has formed a strong bond with his sword, and the sword itself has almost become like another character in the show because of the importance and meaning it holds.