 This reputation seems to have its origins in a legend surrounding the famous warrior Minamoto no Yoshitsune . When Yoshitsune was a young boy going by the name of Ushiwaka @-@ <unk> , his father , <unk> , was assassinated by the Taira clan . Taira no Kiyomori , head of the Taira , allowed the child to survive on the grounds that he be exiled to the temple on Mount Kurama and become a monk . But one day in the <unk> @-@ ga @-@ dani Valley , Ushiwaka encountered the mountain 's tengu , Sōjōbō . This spirit taught the boy the art of swordsmanship so that he might bring vengeance on the Taira . 
