From the game's introduction:

Welcome to a game system that is the first of its kind. 100% Fantasy is a game that you can enjoy with friends, without all of the formulae, complications and memorization needed by typical role-playing games. In this RPG (Role-Playing Game), a Game Designer or GD for short, hosts adventures that take place within his or her imagined setting. It is the Game Designer's first responsibility to interact with the other Game Players or GPs for short at the table - the players that take on the role of Characters composed of a few cards: one Character Card, one Heritage Card, a Defense Card, a Language and Reputation Card, several Weapon Cards and usually a stack of Items Cards that have been instilled with magical powers.

For an ideal play-experience, there are four to eight Game Players with a single Game Designer running the show. When there are more than eight Game Players, it may be advantageous for the Game Designer to have an assistant helper to be privy of the Game Designer's story and plots. The assistant often takes on the role of an antagonist (such as a monster or foe) by acting out the part to enhance the game. Since the GD has minimal downtime during an active game, the assistant can be useful to allow the Game Designer more time to make on-the-fly adjustments to the game when needed.

The Game Designer first prepares each adventure by coming up with various plot-ideas, and crafts interactive situations that may turn the story from emotional reactions to engaging battles and strategic puzzles. Just like a real storybook, the game wisps Game Players into the universe created by the Game Designer. All Character Cards exposes all ways that Game Player can interact with that particular Character (either played by a Game Designer or the Game Players).