After the forced suicide of Nobunaga Oda at the Incident at Honnō-ji, powerful figures Katsuie Shibata, Hideyoshi Toyotomi, Nagahide Niwa and Tsuneoki Ikeda meet to decide on a successor. The conference would become Japan's first group made political decision. The meeting was known as the Kiyosu Kaigi.

National Audit Bureau member Hajime Matsudaira (Shinichi Tsutsumi), Tadako Torii (Haruka Ayase) & Asahi Gainsbourg (Masaki Okada) travel from their homebase of Tokyo to the city of Osaka. Their mission is to discover any financial irregularities & to ensure the correct use of federal money in the Osaka city government. Their initial audits go smoothly, but things turn more interesting once they enter the Karahori shopping district - the area with a long history reaching back to the Meiji era.

In the year 1590, the mighty warlord Toyotomi Hideyoshi is close to fulfilling his ambition of unifying all of Japan under his banner when he comes across unexpected resistance in the form of a floating fortress known as Oshi Castle. Narita Nagachika, a frivolous hedonistic fellow and unlikely candidate for the position of rebel general, finds himself in charge of defending the castle. His odds? An army of 500 men to combat Toyotomi Hideyoshi's army of 20,000.