From the PDF Introduction
A campaign option Web Enhancement for Oriental Adventures
Oriental Adventures includes a featured campaign setting: the world of Rokugan from the Legend of the Five Rings card game and novel line. Rokugan is just one example of the type of campaign you can create and play using the Oriental Adventures rules, however. While Rokugan draws primarily from historical Japan for its cultural influences (and secondarily from other East and Southeast Asian cultures), the scope of Oriental Adventures is broad enough to capture the flavor of nearly any historical or fantasy Asian culture.
Chapter 10 of Oriental Adventures offers a brief example of how a Dungeon Master might go about creating a campaign with a different flavor than Rokugan, using a different subset of the rules options presented in the book. The Mahasarpa ("great serpent") campaign setting is a more fleshed-out treatment of that example, detailing a complete setting that draws from India and Hindu Southeast Asia for its inspiration.