At the dawn of the Meiji period, the Gokumonjou, an inescapable prison, was established in the middle of a vast lake to counter the soaring crime rates brought by the new era. The famous Kumou brothers serve as ferrymen: the eccentric family head, Tenka; the reckless but noble second son, Soramaru; and the guileless youngest, Chuutarou. Despite their grim work, the three lead relatively peaceful lives in the perpetually cloudy town of Oumi, alongside their housekeeper, Shirasu Kinjou. Buried in Oumi's long history 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 Kumou family's true duty 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.