Takashi Shimamura

Shimamura keeps the ordinary look of a Japanese high schooler, marked by dark blue hair and pale blue eyes. Even after his conversion into a post-human, he outwardly passes as a quiet student able to keep attending class.

By nature Shimamura is guarded and solitary, drawn to a classmate he never manages to approach even as a teacher preys on her. A childhood tragedy hardens him: he blames himself for failing to protect his young cousin and absorbs the worldview of an old paratrooper he befriends. That mix of guilt, detachment, and borrowed philosophy sharpens into a conviction that the world's cruelty must be answered, whatever the cost.

Before his transformation, Shimamura lived with his mother, Yoshie Shimamura, and attended a Japanese high school, keeping to himself while quietly caring for a classmate being preyed on by a teacher. One summer his mother sent him to relatives in a mountain village, where his little cousin took to calling him her big brother and he came, in turn, to treat her as a sister. A retired paratrooper he befriended there gave him George Orwell's 1984, which he worked through mostly out of boredom. Everything changed when the two children stumbled on a corrupt officer and a local official hiding a body: the policeman opened fire and killed his cousin before the paratrooper gunned the man down. Shimamura never forgave himself for failing to save her, and the old soldier's grim outlook took root in him.

Back home and visibly shaken, he nursed a wish to rescue his abused classmate yet could never bring himself to act. Soon afterward a rogue American Empire AI known as 1A84 slipped into his cyberbrain and began rebuilding it, a grueling process that left him hallucinating his dead cousin and, at last, picturing paratroopers storming his school and killing him. He emerged from it a post-human.

Now more than human, Shimamura stayed at his school and built Think-Pol, a brain-hacking tool that turned killing into a crowd verdict: users on a hidden website could nominate a target and pile cyberbrain assaults on anyone the crowd voted to condemn. Its first casualty was the teacher who had assaulted his classmate. Unsatisfied by that brand of justice, he set the program loose and slipped out of sight to pursue larger plans with Suzuka Mizukane. Later strikes hit a senior yakuza, disliked celebrities, and the prime minister, though Section 9 blocked the assassination.

When Togusa and Batou investigate his disappearance, Shimamura ghost-hacks Togusa through a flood of his own memories, seizes him, and disables the two escorting Tachikoma to slip away. He abandons Togusa on a train bound for the half-rebuilt ruins of Tokyo, where he and Suzuka have gathered youth, immigrants, and the displaced into a fledgling society called N, every member willingly seeded with his double-think virus, which makes them relive a cherished past while carrying on daily life. As insurance, Suzuka commandeers an American nuclear submarine through a 3D-printed android body tied to both their lives, rigged to launch on either of their deaths.

Section 9 traces Togusa to Tokyo, uncovers the settlement and its nuclear failsafe, and splits up to seize either post-human or to reach the submarine. An American special-operations team lands as well, and after Suzuka slaughters his unit, the mercenary Stan sides with Section 9, turning the fight three ways. Suzuka falls to the Americans, but Shimamura has already handed the trigger to every citizen infected with double-think, then bolted by hijacking a Tachikoma. A resurrected Purin Ezaki, herself now a post-human, is swayed to his cause. He ghost-hacks the team into a simulation in which most of Section 9 dies, while the American Empire firebombs Tokyo with a chemical weapon to smother any launch. Inside the construct the Major kills him as the missiles seemingly fly.

The reality proves gentler: everyone in Tokyo was moved into underground stasis while the chemical agent was deployed, and the double-think infected drift through their fond illusions. Only the Major and the ghost-less Purin can see through it. Purin leads the Major to Shimamura, who has fused himself into the net to finish double-think, and he explains that its layered dream would strip the world of its miseries. He leaves the choice to her: let the system complete, or wrench him out and restore the old reality. The final image is the Major's hand on the cables binding him to the net, and the outcome is left deliberately unclear, hinting that she may have let double-think stand.