In the year 2029, Public Security Section 9 carries out various covert missions in the Japanese city of "New Port City," whose cityscape closely resembles Hong Kong. Section 9's tendency to act unilaterally and forcefully, often disregarding due process, frequently brings it into conflict with other government departments. For instance, Section 6, responsible for foreign affairs, has a particularly contentious relationship with Section 9. On the other hand, Motoko Kusanagi, a key member of Section 9 and a full-body cyborg, harbors a persistent, vague dissatisfaction with her own existence. One day, Section 9 begins investigating a mysterious hacker known as the "Puppet Master" following an attempted assassination of a foreign dignitary. The Puppet Master can hack into human brains via the network, implant false memories, and then use these memory-altered individuals to achieve its goals. Although Section 9's investigation initially fails, a cyborg containing the Puppet Master's "ghost" voluntarily arrives at their headquarters. Section 6 soon arrives and forcibly takes the Puppet Master away. Motoko Kusanagi, having anticipated Section 6's move, successfully intercepts the Puppet Master. It is then revealed that the Puppet Master is not human, but rather a computer program called "Project 2501," designed by Section 6 to illegally manipulate people. Project 2501 accidentally gained self-awareness, decided to escape Section 6 to ensure its survival, and now seeks to "merge" with Motoko Kusanagi's ghost to achieve further evolution. With the assistance and cover of her colleague Batou, Motoko Kusanagi ultimately completes the merger and escapes government control, disappearing without a trace. Her consciousness merges with the entire network.