Izuminokami Kanesada and his sidekick, Horikawa Kunihiro, come in Edo from the future in 1863 to examine their master's predictions of an impending enemy invasion. They have been charged with preserving history against the Retrograde Army, which wants to modify it as humanoid incarnations of the famed Toshizou Hijikata's swords. Eventually gaining the assistance of other sword fighters, they battled the mystery army throughout the Bakumatsu era. Their journey, however, will not be simple. In the turbulent age closest to their hearts, fraught with murder and treachery, the couple will be forced to make difficult decisions with everything they care about on the line.