The Meiji era backdrop feels lived-in, not costume. Three brothers hauling criminals across a lake becomes the frame for something darker: the weight of a bloodline nobody chose, carrying sins that aren't theirs to carry. By episode three you realize the prison itself is a question, and by the finale you understand why these three were never meant to survive it whole.

Japan's Meiji period stripped samurai of their swords and status, and many who refused to accept the change turned against the new government, spreading bloodshed. To hold the lawbreakers, the authorities build a huge prison in the middle of Lake Biwa. Tenka Kumou helps the police catch criminals and ferries them to the prison, assisted by his younger brothers, the ambitious Soramaru and the eager Chuutarou. Alongside former Fuma ninja Shirasu Kinjou, they lead a modest, cheerful life of study and training. Beneath that calm routine, the legend of the Orochi curse stirs in the city of Oumi: every three centuries Orochi is said to be reborn in a human host, a sign of coming disaster. Rival factions hunt for that host, some hoping to seal the curse and others with darker aims. The result is a period action series set against the unrest of the Meiji era.