The player controls a young messenger boy named Knight who is joined by his best friend, a fairy girl named Nehani. While running a routine errand for the mayor, the two stumble upon a small pink monster they later name "Baby". Soon after meeting the creature, Knight has a vision of a spirit who tells him to deliver Baby to an ancient monument called "God's Tower" in order to find its mother. After a few minor setbacks (and the discovery of the mysterious Living Toys, magical dolls that come to life and assist you in battle) the group sets off on its journey.
Along the way, the group runs into several other colorful groups of characters, each of whom are intent on "saving the world" in their own radically different way. The first enigmatic Artema Cult, a network of churches who believe their leader Artema to be a messiah. Soon after the group encounters the pair of Darkbeat, a mercenary who fancies himself "The Chosen One" and has vowed revenge against a man named Karmine, and his sister Ibkee, a kind-hearted dinosaur-like creature who runs an orphanage. The third group of would-be heroes is led by Kalkanor, a pompous royal knight on a journey to collect magic stones in order to imprison a vicious titan called "Xizan".
Though they initially seem unrelated, the paths of these different groups (including your own) gradually become more and more intertwined as the quest goes on, climaxing in the rise of an evil that threatens the entire world. As the future looks more and more bleak, it is up to Knight, Baby, Nehani, and their friends to save the Earth from certain doom.
Source: Wikipedia, "Guardian's Crusade", available under the CC-BY-SA License.