SD-S Island is a small island located between Besmarka, Zoroaster and Shanzhu. It is controlled fully by the Satsujin Double-Six, who use it as their base of operations.
At some point in the past, the original Satsujin family and their forces arrived on the island, and set about making it their base. As it had tennants existing there, in the form of settled Ancorans, the SD-S attacked them. The survivors of the attack were either imprisoned or drafted into the organisation.
The island is currently ruled by the current patriarch of the Satsujin Double-Six, Rokuji Satsujin.
The island has a desert climate, but its inhabitants have developed technology that is able to resist occasional sandstorms.
There is no definitive native species to the island, though it was formerly a colony of settled Ancorans.