In the early 16th century, Japan is a warlike society ruled by samurai and their daimyo warlords. When Portuguese merchants arrive in 1543, they are the first Europeans to set foot in Japan. Missionaries quickly set out to convert the nation to Christianity. In the same year, a samurai boy named Tokugawa Ieyasu is born to a low ranking daimyo family.

To prove his family's loyalty to their ruling warlord, Ieyasu is given as a hostage where he remains for most of his childhood. When he is finally freed, he reclaims his family's domain and allies himself with the most powerful rulers in Japan: Oda Nobunaga, and his successor, Toyotomi Hideyoshi. Hideyoshi awards him a small fishing village named Edo, later to be known as Tokyo, and provides him with a vast area to rule. But Hideyoshi and Ieyasu are uneasy allies.

On his deathbed, Hideyoshi, places Ieyasu in command until Hideyoshi's true heir—his young son, Hideyori—will rule. When daimyo rebels challenge Ieyasu's control, Tokugawa Ieyasu's samurai armies defeat them at the Battle of Sekigahara. The victory brings to Ieyasu the title of shogun. Ieyasu's only remaining obstacle for total control of Japan is Hideyori. In 1614, Ieyasu renounces his allegiance to Hideyori and attacks Osaka Castle, slaughtering more than 100,000. It is the beginning of a dynasty that will endure for more than 250 years.