The fall of the samurai shogunate and the prohibition of swords in the 11th year of the Meiji Era left Japan with long-lasting wounds. Dissatisfied with the recent changes, many former samurai plot against the new leadership, resulting in a wave of carnage. To combat this movement, the government builds a massive jail in the center of Lake Biwa. Tenka Kumou, who is unofficially assigned to assist police in arresting criminals, also works as a ferryman to the Lake Biwa jail with the support of his two younger brothers, the ambitious Soramaru and the joyful Chuutarou. The Kumou brothers, together with former Fuma ninja Shirasu Kinjou, live a thrifty and joyous existence devoted largely to studies and training.