Ryūshin no Tachi

The Ryūshin no Tachi is a special katana that was once owned by Shōyō Kawahiru. According to legend, it was forged from the fangs of a dragon god that watched over the divine tree and protected it from harm. After the death of Shōyō and the subsequent burning of his school, it was recovered by Seireitou Hyūga. He spent years analyzing the special qualities of the blade and happened upon the discovery that the Ryūshin no Tachi possesses the unique power of absorbing the wavelengths of its owner's chakra, essentially drawing it within the blade in order to amplify it, and then rebounding it back onto its user; repeating the process nearly instantaneously until the intensity of the user's chakra becomes so great that they manage to develop supernatural abilities as a result. Of course, he had never actually tested his hypothesis so it is strictly theoretical as to if this is actually how the blade operates.

Following the end of their greatest battle, Seireitou offered the blade to Ryun Uchiha as a gift, believing that the sword's rightful place should be with the one that most best represents the ideals of their late mentor.

Trivia

 * The act of Seireitou giving a sword, that is both precious and serves as a reminder of his mentor, to his long-standing rival Ryun is derived from a similar action done by the Japanese warlord Takeda Shingen to his rival Uesugi Kenshin. Despite being bitter rivals that consistently sought ways to defeat the other, for their own reasons, they were reported to have shown each other tremendous respect and often exchanged gifts.