Despite having owned one of the Possessed for quite some time and being a swordsman – Ginkaku Uneri had a strangely high tolerance for the katana’s poison.
The venom of Kiki Shikizaki’s blades.
A merciless venom that drove swordsmen mad.
That the Great Sword Hunt was the superlative expression of this insanity is not longer a subject of debate – and further to the point, Hakuhei Sabi, extolled as the greatest swordsman in Japan during his day, fell victim to the venom and betrayed Togame and thereby the Owari bakufu. And as we saw in Book One of this saga, even Komori Maniwa –  a ninja, not a swordsman – had not been totally immune to the Leveler’s toxicity.
But Ginkaku Uneri was different.
To be sure, the venom was gnawing at his body, potent as could be – but in terms of personality, there was no perceptible difference between who he was before inheriting the Razor from his father, and who he became thereafter. Mere possession of a Shikizaki blade will drive you to murder – but since Uneri felt the same drive before the Razor fell into his hands, and was alreading killing like it was his job, the sword could not be held accountable. No change transpired when he became the owner – which, for a swordsman of his calliber, was inconceivable. The venom of the Twelve Possessed was that intense.
After all – these were the swords that reigned over the warring states.
In sooth, ten generations back, in the Age of Warring States, the sword’s poison had overmastered Uneri’s forebear Kinkaku Uneri, permeating every nook and cranny of his body – how else could he have been so insubordinate, in his refusal to hand over the sword, as to make an enemy of the daimyo of Tottori and the Old Shogun, unifier of the nation? Even Ginkaku Uneri, at a remove of so many generations, suspected the account of the ten thousand slain was hogwash, but the madness had not stopped with Kinkaku: for henceforth, every son of the Uneri who came into possession of the Razor, all the way down to Ginkaku’s own father, was incontrovertibly deranged.
Crazed from the venom of the Razor.

Katanagatari Omnibus 1, Page 176