In the end, there was only one reason for Komori’s defeat. Nanami’s confidence in her brother notwithstanding, no one would normally expect a veteran Maniwa to lose to a novice Yasuri.
But lost he had.
And Zetto the Leveler was to blame.
He just could not resist – using the katana.
Maybe the Hell-Made was simply being servicable the first time – and so could maintain self-control. Still, even if his Star Cannon was depleted, Komori – a ninja, not a swordsman – reached again and again for the Leveler: proof that the sword’s poison was coursing through his veins… as wary of this as he had been.
The venom of the Possessed.
Owning one made you want to kill –

Katanagatari Omnibus 1, Page 93