Of course – the fact that the Kiku was not merely meant for breaking swords, but was devised by the school’s founder Kazune Yasuri, working in concert with Kiki Shikizaki, specifically for breaking Zetto the Leveler, the hardest sword in all the land – and the fact that Shichika had only been unable to break Zetto the Leveler on Haphazard Island because his battle experience was nil, and his skills too green, were more than he could hope to understand.

Katanagatari Omnibus 4, Page 277