A former japanese reincarnated into a mysterious sword which slept on a pedestal in the middle of some hidden ruins. After "awakening," the sword quickly learned to both move and fight on its own by using magic, and that it had the ability to absorb a monster's core to raise its strength.

After building up some power, it grew bored and decided to depart the ruins to explore new lands, but got stuck on a mana-depleting zone and lost its freedom for several weeks. Eventually, a black cat beastkin slave found it by chance while fleeing from a monster and the sword helped her regain her freedom. As a result both decided to continue together and the sword bestowed the girl with a name (Fran) and a contract which shares its abilities with her. Fran in return named the sword Shishou (Master).

Shishou eventually also summons a familiar and names it Urushi, which ends up as Fran's familiar as well.

He also gains the ability to create doppelgangers of himself, which look like his former human self.

(Source: Novel/Manga)