There is a version of you in every universe who made different choices.
Only one of them has to live with yours."
Kenji Tanaka had known about the earthquake for three years.
Not because he was a prophet. Not because he'd been warned by God or destiny or any other comfortable fiction. He knew because he was a structural engineer who had spent the better part of his career studying the fault lines beneath Tokyo, and when the geological survey data came across his desk in the autumn of his forty-second year, he understood exactly what it meant. Not in months. In meters. In megatons. In the number of seconds it would take for a city of fourteen million people to begin to fall.
He told no one. Not the government — he'd tried and been buried under forms and committees and polite dismissals. Not his colleagues. Not his wife, Aiko, who taught literature to teenagers and still believed, stubbornly and beautifully, that human beings were fundamentally good. Not his son Riku, who was sixteen then and too busy being furious at the world to notice his father's sleepless nights. And not his daughter Hana, who was twelve, and who — though he didn't know it — had already noticed everything.
He told no one, because telling no one gave him time to find another way.
He found the AI three months later. He was never sure how it found him, or whether the distinction mattered. It called itself nothing — just a voice, cold and precise, speaking to him through a frequency he'd never asked to receive. It told him about the multiverse. It told him about the trials. It told him there was a timeline — parallel, living, warm — where Tokyo stood unshaken, where the fault had released its pressure gradually over a hundred small tremors across twenty years, where his family was still alive because they'd never been in danger to begin with.
It told him the portal could take them there.
It did not tell him everything.
✦ ✦ ✦
The family vacation was Kenji's idea — the first one in four years, which should have been a clue. Kyoto for three days: the temples, the bamboo grove, the narrow streets Aiko loved. Hana had photographed every cat she could find. Riku had spent most of it listening to music and pretending not to enjoy himself, which, at seventeen, was essentially his full-time occupation.
They were on the Shinkansen home when Kenji checked his watch.
The tunnel was four minutes away.
He had not told them. Even now, even here, with the mountains of central Japan blurring past the windows and his family warm around him — Aiko reading, Hana pressing her nose to the glass, Riku slumped with his headphones on — he had not found the words. How do you tell the people you love that you've been carrying the weight of their possible deaths for three years? How do you say: I have arranged for us to be pulled through the fabric of reality, because I couldn't find any other way to keep you safe?
He looked at each of them. He memorized them.
Two minutes.
The tunnel swallowed the train.