Osa is part of Okayama Prefecture and the sub-prefecture called Atetsu. It is a mountain town, accessible until recently by only one two-lane road from the city known as Niimi, where Osa's children go to high school and can attend the small college there recently upgraded from junior college status. One of the principal trees is the hinoki, or Japanese cypress, with its beautiful evergreen foliage.
Panelling made from hinoki wood has a fragrance often compared with that of sandalwood.
Its mountainous landscape is particularly suited to handgliding, and town publicity calls attention to the winds that rise off local slopes. Cabins, trailer camps and other accommodations are in various stages of development to attract visitors. Its area is 121.25 square kilometers, and it lies along the Osakabe River, which runs south to join the Takahashi River, one of the three great rivers of the Prefecture. Its altitude at its center is 350 meters above sea level, and its farmland varies from 250 meters to 600 meters on its Dainichi Takahara plain. The town's landmark, Mount Osa, rises to 988 meters, but there are nine other prominences that are more or less 1,000 meters high.