The game is set in an alternate reality, in which Tokyo is invaded by hordes
of demons. You play the role of a young man who lives in an underground
shelter and is training to become a demon hunter with help of special
programs. One day, during a training, one of the programs goes berserk, and as
a result you are thrown into the world where you must fight for your life
against vicious demons.

Giten Megami Tensei: Tokyo Mokushiroku is a non-canonical part of Megaten
universe, featuring recurrent setting and story elements of the franchise.
Like in classic Shin Megami Tensei games, the largest part of the game is
spent in 3D dungeons, which are viewed from first-person perspective. The
battle system introduces some unusual elements: enemies are visible before the
actual battle begins, and during your dungeon exploration, you will be
sometimes attacked from different sides. You will have to turn around to face
the enemy in real time, but the game will be paused when you select commands
from menu, in a traditional turn-based fashion.