This is a prequel to the two Langrisser games (the first one is known in the US as Warsong). The events of the third game occur thousand years before those described in the first "Langrisser". The story centers around the creation of a holy sword named Langrisser, and the first Descendants of Light, the only people who can wield it. The main character is the knight Diharuto, the ancestor of Leon (Elwin's rival in "Langrisser II"). He must defeat the evil Boser, who is bound to the evil sword Alhazzard.

In Langrisser III, you don't control whole armies, but only their generals, whom you move around the battle field. Once two enemy generals meet each other, a 3D battle sequence occurs, during which the two armies fight; the outcome of the battle is decided only by the victory or defeat of the general. The game also features love simulation elements: depending on the main hero's responses to various female characters, you can raise their "love level".