This ken, or double-edged sword was treasured by Tachibana Muneshige, the first lord of the Yanagawa domain. It has been passed down in the Tachibana family with a tradition that says that on the day young Muneshige was adopted by Bekki Dousetsu at the age of 15, this sword was given to him from his father Takahashi Joun with the words-”if we should ever fight on opposite sides, you should be the head of the army that would kill me, or otherwise you should commit suicide bravely with this sword.” Since then, Muneshige always carried it on him as a keepsake from his father. Later, Takahashi Joun was defeated in a battle and killed himself in his Iwaya Castle when Muneshige was twenty.
The creator of this sword, Nagamitsu, was an outstanding swordsmith in Bizen Province, located in present-day Okayama Prefecture, in the 13th century during the late Kamakura period. The gentle curved blade tip is a feature of the Kamakura period style. There are few remaining ken swords created by Nagamitsu. This valuable sword was designated as an Important Cultural Property in 1937.