Shin Megami Tensei is an RPG set before and after the destruction of modern Tokyo. The player character gains the ability to recruit demons via a mysterious Devil Summoning Program, only to witness the city be destroyed by warfare between humans and demons. Two powerful new factions vie for control of Tokyo: the lawful Messians who value order above personal freedom, and the chaotic Gaians who embrace free will even if it means survival of the fittest.
Amidst this power struggle, the player must determine the course they wish humanity to take whether it be through joining one of the factions, or even attempting to oppose them both in order to forge their own path.
Shin Megami Tensei plays like a traditional RPG complete with dungeon crawling and exploration from a first-person perspective. Enemies are encountered randomly, leading to turn-based battle sequences which are also conducted from a first-person viewpoint. Players must assemble a party of up to six characters including any demons they have recruited to their cause through coercion or even bribery.
Demons are registered to the player's special computer, and can be summoned later to accompany them throughout the game through an in-game fee. Players must pay an additional upkeep of Magnetite in order to keep demons active in their party. Demons fall into one of three alignments (Law, Neutral and Chaos), and summoning them will have an affect on the player character's own alignment.
Decisions made by the player throughout the game with respect to the opposing factions will also play a major part in determining their alignment, ultimately determining which one of several endings await them once they complete the main scenario. The importance of player alignment would eventually become a series staple, factoring heavily in the way players will play their game.