Onimusha: Warlords is set in 16th century Japan during the period of the civil war dominated by Nobunaga Oda. You play Samanosuke Akechi, who dies during an attempt to stop the kidnapping of young princess Yuki, the sister to Yoshitatsu Saito. However, Akechi is given another chance at life, and is handed the gauntlet of the Ogres.
With this new power Samanosuke must fight through the monster-filled halls of Inabayama Castle. As monsters are defeated, their souls are absorbed by the gauntlet, increasing its power. Some souls restore Samanosuke's health and magic, while others can be used to power up weapons, armor, and items. Powering up weapons will increase their damage and the strength of their associated magic, and is also required to pass by special locks throughout the castle. Items will need to be found in one part of the castle to unlock doors or otherwise bypass obstacles elsewhere in the castle, and sometimes the player will take control of Samanosuke's companion Kaede while Samanosuke is incapacitated in some way. Kaede can reach some locations that are beyond Samanosuke as well as pick locks and throw kunai, but she can not absorb souls or open any lock intended for the wearer of the Ogre gauntlet.