In the dawn of the Meiji period, the Gokumonjou, an inescapable prison, has been established in the middle of an enormous lake to counter the soaring crime rates the new era has brought. Serving as the ferrymen are the famous Kumou brothers: the eccentric family head, Tenka; the reckless but noble second son, Soramaru; and the guileless youngest, Chuutarou. In spite of their grim work, the three lead relatively peaceful lives in the ever-cloudy town of Oumi, together with their housekeeper, Shirasu Kinjou.
But buried in the long history of Oumi is the legend of the terrifying "Orochi," a serpentine beast that awakens every three hundred years in a human vessel. Unbeknownst to Soramaru and Chuutarou, the actual job of the Kumou family is to seal the Orochi away before it fully revives—or the world will be plunged into destruction. Amid the monster's next resurrection, the Kumou family must find the resolve to keep laughing under the clouds.