Hisui is the ancient name of the region explored in Pokémon Legends: Arceus.
The game is set in a historical period long before the events of Pokémon Diamond and Pearl. Hisui is the same broad land that later becomes known as the Sinnoh region, but it is portrayed before modern towns, Pokémon Gyms, and the established Pokémon League have developed.
Players join the Galaxy Expedition Team and work from Jubilife Village while surveying Pokémon in large open areas. The game emphasizes observing, catching, and researching Pokémon, making the creation of the region’s first Pokédex a central objective. It also introduces regional forms and evolutions, including Hisuian Zorua, Hisuian Growlithe, and Wyrdeer.
The distinction between Hisui and Sinnoh is important. Sinnoh is the name used for the region in the later-era Diamond, Pearl, and Platinum stories, while Hisui identifies its earlier historical form. Pokémon Legends: Arceus therefore functions as a prequel to the Sinnoh games rather than a separate unrelated region.