IMDB’s description
Hired as a mercenary unit, the former members of Japan’s elite Section 9 are faced with the sudden appearance of “Post-Human,” a being with tremendous intelligence and physical capabilities.
This is the new Ghost in the Shell series on Netflix. SAC stands for Stand Alone Complex, which is an alternate continuity to the main stream versions people might be familiar with from the original Anime movie or from the recent 2017 live action version. This continuity is different in that section 9 has apparently been disbanded, with most of its members working as mercenaries in various countries. A new global threat to humanity, called “Post-Humans” surfaces, and this brings the team back together under the Japanese government to recreate Section 9.