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.