This warrants a brief explanation of who Kiki Shikizaki was.
It happened before the Owari Bakufu had formed a body politic of peace and order, when Japan was caught in what was called the Age of Warring States – a rumor began to spread among the swordsmen on the fields of war.
The rumor involving swords.
The gist was that by wielding a katana fashioned by this crazy swordsmith, a lone wolf who belonged to no tradition, you would be invested with the power to take on a whole army – while on the flipside, were you to face a swordsman bearing a katana made by the same swordsmith, you would have no hope of winning and be forced to flee –
These swords were called the Mutant Blades.
And the swordsmith was named Kiki Shikizaki.
He made exactly one thousand Mutant Blades.
In the battles between states, the number of Mutant Blades held by a power is said to have been the deciding factor – and in practice, this was true.
The clashes between the twenty-five states of the period were all biased by the number of Mutant Blades.
The Great Unifier – known today as the Old Shogun, came out of the war with five hundred and seven Mutant Blades.
His appetite for these swords was insatiable.
With that many, it would have been stranger had he failed to rule the land – perhaps.

Katanagatari Omnibus 3, Page 217