Hyoma, the protagonist, has a dream of another world over a pillar of light coming from his family shrine that has been missing since his ancestor's time. The next day, he decides to take his two friends, Shizuku and Hayatemaru, to investigate the mountains where his dream took place. During their investigation, they find a cave with strange technology but as they are looking into it, the machines activate and a bright light appears, taking them to another world known as Endia.
Chaos Wars is a crossover between several companies' role-playing video game series, including Aruze's Shadow Hearts, Atlus's Growlanser, Idea Factory's Blazing Souls, Spectral Souls: Resurrection of the Ethereal Empires, and RED Entertainment's Gungrave and Code of the Samurai.
Source: Wikipedia, "Chaos Wars", available under the CC-BY-SA License.