The fourth installment of the sci-fi RPG series comes in two parts, this game being the first. In it, the player once again takes control of the original hero of the series, the cosmic hunter Yū, his lovely female comrade Saya, and their friends. Something is wrong on the planet Kazarin: the princess Saria was kidnapped, and Yū arrives on the planet to look closer into that matter, while Saya agrees to impersonate the princess for a while to ensure a calm investigation. However, their quest goes far beyond the kidnapping investigation: soon they will have to face the four heavenly kings, demons who control the elements from which the universe is built.
The game features a role-playing system similar to the first three installments of the series and other Japanese RPGs: the player navigates a party of characters (up to four active combatants) around the top-down overworld, visiting towns, buying equipment, descending into dungeons, and fighting random enemies in turn-based combat viewed from first-person perspective. A new introduction to the series is an ATB (active-time battle) bar (which came to prominence after having been first implemented by Final Fantasy IV): the player can only execute an action when the bar of the character in question is filled; therefore, switching between characters and reacting quickly becomes a necessity. The game begins with a "digital comic" introduction typical for most Japanese adventures (with menu commands to interact with still anime-style pictures); however, this gameplay mode disappears shortly afterwards and plays no further role.
The mild erotic elements characteristic of the previous episodes have been somewhat intensified in this installment; a few scenes feature nudity in context of a sexual situation.