The world of Arc: Twilight of the Spirits is populated by two races: human and Deimos. The two races prefer to avoid contact with each other, but both depend on the Spirit Stones to sustain the balance in the world. Recently, the human army began sweeping across the lands, taking over countries. This army is going after the five great Spirit Stones. The Spirits, however, are determined to prevent this; to achieve their goal, they choose two heroes who would eventually be able to unite the two races in a battle for justice. One of them a is a human nobleman named Kharg, who hates the Deimos and is planning revenge; another is a Deimos slave named Darc, who dreams of uniting and commanding his race. Will the two heroes be able to put aside their differences and save the world?..

Arc: Twilight of the Spirits is the fourth entry in the Arc the Lad series. Like its two immediate predecessors, the game has tactical battles which allow free positioning and movement of the characters on the combat field. However, the game is closer to being a “regular” Japanese-style role-playing game rather than a tactical RPG. The player controls a relatively small party (up to six active combatants), and is able to explore towns and dungeons in a standard RPG fashion. In the beginning, the game puts the player into control of Kharg, but afterwards the chapters alternate between the human hero and Darc, each with his own party. Characters can use a variety of techniques, accumulating SP (spirit points) in battles and them using them to learn special attacks.