He is a dagger, the dagger of the Sanjo family.
It was originally dedicated to Mount Kurama by Sanjo Munechika as a way to pray to gods and Buddhas.
The name was given by the monks in the temple at that time, and was later given to Minamoto Yoshitsune by Tokobo Rennin, the abbot of Kurama Temple, and he followed Minamoto Yoshitsune throughout his life.
"I, Kon-ken! I am Lord Yoshitsune's guardian sword! What, it's awesome!"
"Please play with me today~"
Concept: Every sword is unique, just like there are no two identical leaves in the world...