In January of 2001, Capcom released Onimusha. And, in the same month, it became the PS2's first 1 million seller.
Source: Capcom Co., Ltd.'s Corporate Page
"Onimusha" is Japanese for 'demon warrior'. Surprisingly, the name is applicable to a number of characters in the story...even the hero...
Onimusha places itself within historical context by including some real historical figures. Oda Nobunaga and Toyotomi Hideyoshi show up as villains, while Imagawa Yoshitomo makes a very brief, and final appearance in the introduction movie. Even the hero is the nephew of Akechi Mitsuhide, the infamous retainer of Nobunaga who eventually betrayed him.
While tales attribute Nobunaga's ruthlessness to some evil or demonic nature, the events of the game are, of course, completely fictional (aside from Nobunaga's attack on Yoshitomo's troops).