Katanagatari centers on Shichika Yasuri, the seventh head of the Kyotoryuu; the sword-less school of Japanese sword martial arts. One day, Shogunate strategist Togame arrives on the island where Shichika and his older sister Nanami live to hire him.
Togame tells Shichika that she is on a mission to find and collect the final twelve swords forged by a master swordsmith by the name of Kiki Shikizaki; with powers so extraordinary, one man could defeat small armies.
With Togame's full intentions, Shichika falls for her and leaves the island to embark on a sword-hunting journey all over Edo Japan.