Kessen III (決戦, Kessen Suri) is a PlayStation 2 video-game produced by Koei and is based on the life of Oda Nobunaga.
The game's time frame is roughly between the years 1560 to 1590. Contrary to many stories and portrayals that depict him as a villain or demon, Nobunaga is depicted in a more virtuous and ultimately tragic light, making Kessen III rather unusual in relation to other video games based in the same era. It is a heavily fantasized and romanticized depiction of his life, although unlike games such as the Samurai Warriors series it goes into more specific historical details. For example, the existence of the Ashikaga shogunate and Nobunaga's relationship is covered herein but completely omitted from the Samurai Warriors games.
The game paints a positive picture of Nobunaga's life, and then enters a "What If" scenario showing what might have happened if he had survived the betrayal by Akechi Mitsuhide. It describes Nobunaga regaining his power base, and then defeating Shogunate forces led by the Akechi clan and other clans of Western Japan on the shores of Kyūshū, with Nobunaga presumably becoming the new leader.
Tokugawa Ieyasu is in this game, presented as Nobunaga's mild mannered and dedicated ally, but is shown flying into a rage when he learns that Nobunaga survives his betrayal, believing that he was going to carry out Nobunaga's destiny. Toyotomi Hideyoshi is also shown, under the name of Hideyoshi Hashiba. His unlikely charisma inspires his troops after he is wrongly told of Nobunaga's death, which leads his friend to comment, "Maybe he would be the one to unite Japan, if Lord Oda was dead."
The game also lets you fight battles against other notable daimyo, like Uesugi Kenshin and Takeda Shingen.
There is a certain level of inaccuracy, due not only to the fantasy element, but also due to the appearance of Miyamoto Musashi, who hadn't yet been born when Nobunaga committed seppuku.
Source: Wikipedia, "Kessen III," available under the CC-BY-SA License.