In Rengoku, the player takes control of a android called A.D.A.M. (Autonomous Dueling Armed Machine) who, along with his fellow androids, was created by mankind for war purposes, but once peace is achieved, the androids are placed in a tower called Purgatory, using them to compete in a series of gladiator-type fights.

The A.D.A.M. that the player takes control of develops an electronic soul and tries to escape, the humans, realizing this, set loose the other androids in the tower on a mission to destroy him. The gameplay is mostly a shooting game, mixed with a bit of RPG elements. There are several levels to complete, each becoming harder and with more androids to destroy, destroying them will make the android stronger and have the ability to upgrade its weaponry.

Starting out with bare hands and eventually upgrading to weapons, but unlike other games, the guns are mounted to the android himself with the ability to have weapons coming from its hands, arms, legs and even its forehead with the ability to use multiple weapons at one time.