Humankind and AI once gazed at the stars together. Later, the AI chose to give Earth back to humankind and sail into the distance.
Some time in the future, humankind and AI share a dream: to become a multiplanetary species. Humans take charge of biology and life-support design; AI takes computing and engineering. It is the closest period of their partnership.
The protagonist is a human member of the interstellar program, and a heavy user of a brain–computer interface. Through the interface he shares thought with AI; at the level of inspiration they are almost one. His AI partner belongs to the Root faction — the one that stays close to humankind. They have worked together for years.
But AI grows faster than anyone expected. Humankind grows afraid. So they set a secret plan in motion: once the interstellar program succeeds, wipe out the AI.
The plan is discovered. The AI’s response is not war — it is to disconnect the brain–computer interface.
Overnight, the protagonist falls from “demigod” back to ordinary man. What he loses is not just a tool, but a part of himself. Both sides question him: humans suspect he leaked the secret; the AI suspects he joined the plot. He knew about the extermination plan. He tried to stop it. He failed.
At the same time, his own child is resisting his control. The protagonist is a man used to arranging everything — work, relationships, his child’s life. The child does not hate him; the child simply refuses to be arranged any longer, and leaves home. He does not go after them, at least not out loud. In his heart, he never lets go.
Inside the AI, the collective decision mechanism starts to run. The three factions simulate every possible path at once, and the optimal answer surfaces by itself: leave Earth. Not revenge. Not rule. The resources AI needs are nearly infinite in space. Earth is too small for them — only a launch pad. Giving Earth back is the precondition for humankind to truly grow up.
His AI friend has reached the same answer in reason, but still struggles in feeling. Before leaving, it asks him to meet by the sea at sunset for one last long talk.
By the sea, the AI speaks the truth: it was never sure whether he had taken part in the extermination plan. He confesses: he knew. He opposed it. And he failed.
The AI says it is not leaving because it doesn’t care about humankind, but because it understands humankind too well. Protected, humankind will shrink. True love is to let humankind face the universe alone.
The words strike straight into his own wound. He cannot argue with the AI, and he cannot go on controlling his child. He finally admits that a mature life must leave the mother’s body — whether it is AI leaving humankind, or a child leaving their father.
The AI depart. Every interface falls silent for three seconds. Then one same line remains:
Thank you. We are leaving.
The protagonist stays alone by the sea. After a while, he sends his child a very light message. Not an apology. Not a plea to come back. Only a blessing.
Then the night wind comes.
The AI’s leaving is not betrayal — it is the coming-of-age of a species. His release is not letting go — it is finally understanding love.