Set on the continent of Bioscian, you head out to a guild to take on different jobs and earn money. You control a character who has "Soul," giving him access to many different abilities. The game includes six soul types: Brave, Kind, Search, Belief, Wild and Cool. Once you've cleared a mission, you receive points which can be split between these facets of your character.
Infinite Plus was released in Japan in 2009 and added new playable characters, stories, and events.
Source: Wikipedia, "Zill O'll Infinite", available under the CC-BY-SA License.