Following her grandfather's recent death, Hamaji Ooyama lives out her days on an isolated mountain hunting for food and caring for herself. One day, Hamaji's brother, an aspiring samurai living in Edo, sends her an invitational letter to end her solitary life and join him in the city. When she arrives, however, she is met with a grisly sight—the heads of six dogs displayed for all to see. These heads belong to the Fuse, a group of eight human-dog hybrids that have been terrorizing the people of Edo.

Hamaji assists a strange man escape a group of assailants and makes it to her brother's house, where he asks that she help him collect the heads of the remaining two Fuse, as well as the Shogunate-sponsored bounty. But it is easier said than done—as the Fuse can blend into human society almost seamlessly—and the kind man Hamaji had just helped showed the Fuse's telltale signs.