S.D. Codified Laws § 47-1A-805

The terms of the initial directors of a corporation expire at the first shareholders' meeting at which directors are elected. The term of any other director expires at the next annual shareholders' meeting following the director's election unless the terms of the directors are staggered under § 47-1A-806. A decrease in the number of directors does not shorten an incumbent director's term. The term of a director elected to fill a vacancy expires at the next shareholders' meeting at which directors are elected. Despite the expiration of a director's term, a director continues to serve until a successor is elected and qualifies or until there is a decrease in the number of directors.