Taken from the Onimusha Wikia:
Onimusha: Soul is Capcom's first browser game, and the first browser game of the series that was released on June 28, 2012. The browser game is a "Sengoku simulation RPG."
The game has players taking up the role of feudal lords during the Warring States period of Japan, using "their powers to achieve the growth of their respective states and train military commanders as they fight with other players."
Read the full article.