The game is set in a fantasy world with medieval Japanese themes, particularly regarding Shinto. Warriors known as mononofu specialize in fighting oni, and form teams to hunt them. Eight years prior to the commencement of the story, a great demon emerged from the underworld and brought an era of calamity to the land of Nakatsu Kuni, which was traditionally protected by the mononofu since ancient times. The protagonist and main characters reside at Utakata Village, one of the final lines of defense against the demons.
Each player can customize their choice of weapons, armor and skills. Special abilities can be obtained through the usage of souls, or mitama, which can be collected during the progress of the game. These mitama can level up by gaining experience from battles, or by paying a certain sum of haku. Different mitama have abilities with various characteristics, and can be categorised into various groups such as offensive, defensive, or recovery mitama. Upon slaying a monster, the players or NPCs can "purify" the monster, which collects items useful in upgrading weapons and armor. Monsters fall into the categories of small and large oni, with large oni being the boss-type enemies within the game.
Toukiden: Kiwami is an enhanced and expanded Toukiden: The Age of Demons. The protagonist's home and its habitants have been protected and three months pass until a new threat emerges. The protagonist must work with different factions to fight against a giant demon swarm. The game features twice the number of demons, two new characters, extended story and new equipment. Additional weapons introduced in the new version include firearms, naginata and kanabō. In addition, there are new character abilities.