At the onset of the Meiji era, a formidable prison named Gokumonjou has been constructed in the center of a vast lake to address the rising crime rates of the new age. The task of ferrying prisoners falls to the renowned Kumou siblings: Tenka, the quirky head of the family; Soramaru, the daring yet honorable middle brother; and Chuutarou, the innocent youngest. Despite their grim duties, the trio enjoys a relatively tranquil existence in the perpetually overcast town of Oumi, alongside their housekeeper, Shirasu Kinjou. However, hidden within Oumi’s ancient history is the tale of the fearsome “Orochi,” a dragon-like creature that reawakens every three centuries within a human host. Unknown to Soramaru and Chuutarou, the true mission of the Kumou family is to confine the Orochi before it fully emerges, as failure to do so would spell disaster for the world. As the time for the monster’s reawakening approaches, the Kumou family must muster the courage to continue smiling beneath the clouds.