When you're the best fighter around, you'd better be prepared to prove it! No sooner was a new security escort for the Imperial Governor chosen, then he was challenged to a duel and slain right before his family's eyes by a mysterious travelling swordsman known only as The Thunder Sword who disappears never to be heard from again.

No one in their right mind would mess with the house of the 13 sisters. So when a corrupt local lord thinks he's made himself a harem overnight by kidnapping 12 of the 13 sisters, he and his partners in crime soon learn that they are the ones who will need defending. But they'll soon find out that they are the ones who will need rescuing from the wrath of number 13!