The revised specifications took four days.
Four days of the two Kenjis working at Reiko's kitchen table in rotating shifts — one sleeping while the other worked, trading the notebook back and forth, building a calculation that was better than either of them would have produced alone because the transit-Kenji had the portal physics and the timeline-Kenji had twenty years of detailed local survey data that turned out to be more relevant than anyone had predicted.
The family, in the meantime, began the work of becoming new people in a new city.
Aiko went to the apartment in Bunkyo on the second day. She went alone — Kenji was mid-calculation and she told him it was fine, she'd handled apartment move-ins without him before, which was true and also, she knew, the kind of thing that needed doing to make the new life real. You didn't make a life by thinking about making it. You made it by going to the apartment and opening the windows and standing in the kitchen for a moment with your hands on the counter and thinking: this is mine.
The apartment was everything the documentation promised: third floor, corner unit, post-2000 construction, two bedrooms and a third smaller room that could be a study, with a view onto a street of ginkgo trees and a convenience store that was, she noted, a Family Mart this time.
She stood at the window for a while.
She thought about the other Aiko, on the bridge, saying: I've been holding things together for long enough. She thought about the specific quality of that sentence — the relief in it, the permission that the other version of herself had given to the existence she had been waiting to live.
She thought: I am here. I am safe. My children are safe. My husband is in a kitchen two kilometers away being infuriated by a version of himself and they are fixing things together. This is what good looks like. I am going to be very angry about the three years for a while, and I am going to be very in love with my husband for a while, and those two things are going to coexist messily for some time, and that is the correct shape for it to have.
She went back to the window and looked at the ginkgo trees and felt, slowly and imperfectly and for the first time in a long time, safe.
Hana and Mei, who had been assigned the same bedroom and the same school district and were therefore required to coexist, discovered that they were significantly more compatible than either would have predicted.
Mei had thirty-one subjective years of experience in a silent forest and had developed, as a result, the capacity to be present in a room without demanding anything from it. Hana had thirteen years of careful observation and had developed, as a result, the capacity to be present in a room without demanding anything from it. They spent the first two days in adjacent silences that gradually became shared silences and then, on the evening of the second day, became a conversation.
The conversation was about the cat taxonomy.
Hana showed Mei the spreadsheet. Mei examined it with the serious attention she gave everything — the attention of someone who has learned that all systems of organization contain a theory of value, that how you categorize a thing says something about what you believe the thing is for.
"Your primary taxonomy is morphological," Mei said. "Ear shape, eye color, tail position. But you have a secondary column — 'behavior observed' — which is functional. You're running two classification systems simultaneously."
"Yes. Because morphology tells you what a cat is, but behavior tells you what it's doing. And sometimes what it's doing changes what it is."
Mei looked at her. The old eyes, very serious. "That's the whole problem with the trial system," she said. "In the forest. The trees classified the people by what they were — their resonance signature, their family relationship, their origin timeline. But the forest didn't have a column for what they were doing."
"Sora was doing the work," Hana said. "For three years. Being useful."
"Yes. And the system classified her as 'incomplete trial' for three years because it was looking at what she was, not what she was doing. Which is" — Mei touched the tablet screen — "exactly the error your secondary column corrects for."
Hana looked at the spreadsheet. She thought about Sora's name carved in bark. She thought about the system and its classification errors and what it would mean to build something better.
She added a third column to the spreadsheet and labeled it: EVIDENCE OF CHOICE.
Riku and Keisuke, the two versions of the same boy, spent the first four days in the careful, observational orbit of two people who want to understand each other and are not quite sure it's allowed. They were assigned to different school districts — Riku to a school in Bunkyo near the apartment, Keisuke to a school in Koenji — and the necessary distance meant that their proximity at Reiko's house had a defined end date, which gave their conversations a slight urgency.
They talked about music mostly, which was the territory least likely to produce the uncanny valley of talking to yourself. Their taste was broadly the same and specifically different in ways that seemed to reflect the divergence: Riku liked music that was heavy and structured, the kind with architecture in it. Keisuke liked music that was more open, less resolved, the kind that sits in the minor key longer than comfortable.
"What happened to the music, after —" Riku stopped. He hadn't intended to ask directly. He'd been approaching it sideways for two days.
"After Dad died?" Keisuke said it the way he said most things: directly, without making it a performance of either pain or control. "I stopped listening for a few months. Not because I decided to. Because none of it was the right shape anymore."
"And then?"
"And then I started listening to things I'd never heard before. Things I had no associations for. It helped."
Riku absorbed this. "I'm sorry," he said.
"You don't need to —"
"Not as a formality. I mean it. I'm sorry that happened to you."
Keisuke looked at him. Something passed between them that was stranger than looking in a mirror — it was looking at a mirror and having the mirror look back with actual recognition, with the particular quality of being seen by someone who shares your interior architecture.
"I know," Keisuke said. "I can tell."
On the fourth day, the specifications were finished.
Transit-Kenji and timeline-Kenji came out of the kitchen at seven in the morning, looking like men who had not slept enough, and laid the completed notebook on the main room table.
"The Sumida River window can process seventy families per transit event," transit-Kenji said. "Forty percent more than the mountain tunnel window. The coherence time is ninety minutes per window."
"The activation sequence is different from the tunnel window," timeline-Kenji said. "It requires a physical anchor point at the bridge — a resonance emitter installed in the infrastructure of the bridge itself. I can install it. I have the survey data and the bridge access."
"How long?"
Timeline-Kenji looked at the date. "Fourteen days. Working normally, with the right materials. The bridge has a maintenance access scheduled in eleven days — I can incorporate it."
"Eleven days. The earthquake projection is —"
"Eighteen days at the outer confidence interval. Eleven for the install, three days of calibration after. That puts us at fourteen days before the earthquake window closes. A margin of four."
"Four days is not a comfortable margin."
"No. But it's a margin." Timeline-Kenji looked at his counterpart. "There is one other thing."
"Tell me."
— ✦ —
"The installation requires resonance signature encoding — building the portal frequency into the physical anchor point. The anchor frequency has to match the operator." A pause. "The mountain tunnel portal was built with your signature — the other-you, the anchor. The Sumida River window, if I'm installing it, will encode my signature." Silence. "Which means this portal runs under my authorization," the timeline-Kenji said. "Independently. Not as a branch of the existing system." "Yes." "A second system. Separate anchor. Separate frequency. But moving people to the same destination." "The same destination, yes." "Which means if something goes wrong with your system —" "My system continues to operate. And if something goes wrong with yours —" "Mine continues." They looked at each other: two versions of the same man, each one the backup for the other, each one the thing the other didn't have — until now. "All right," the timeline-Kenji said. Then: "Your daughter's message arrived this morning, by the way. Through the system's internal communication channel. She sent coordinates." He held up his phone, displaying a precise location: 35.6892° N, 139.7917° E. The Sumida River bridge, Koto Ward side. Below the coordinates, a message in Hana's handwriting, transmitted somehow from the transit documentation system to an address Kenji had not known it had access to. The message read: Tomoko was here. She's marked the spot. She says there are seven hundred families in her immediate neighborhood who need to know about the window, and she's going to tell all of them.