The story for the Rise of the Kasai takes place in a Polynesian-influenced fantasy setting. The plot centers on a band of warriors known as the Rakus and their battles against the evil sect of dark magicians known as the Kasai. The narrative focuses on a series of events that take place ten years prior to the events of The Mark of Kri and ten years afterward.
The player first takes control of Baumusu and Griz through the timeline of events ten years prior to the Mark of Kri, to discover what exactly happened to Rau (the hero of The Mark of Kri). Then, he takes control of Rau and Tati to find out what happens in the decade that follows the events of The Mark of Kri.
The combat system of Rise of the Kasai revolves around the use of Focus Beams, a gameplay mechanic used to lock on to single or multiple enemies coming from any direction.
Source: Wikipedia, "Rise of the Kasai," available under the CC-BY-SA License.