The voice was Riku's voice.
Not Riku's voice exactly — Riku was standing to Kenji's left, very still, staring at the portal with the expression of someone whose mind is running fast through a set of implications and not yet reaching the end of them. The voice through the portal had his tonal quality, his specific rhythm, the precise weight he put on single-syllable words. But it had something else: age. This voice was older. Older and rougher and carrying a tiredness that had nothing to do with sleeplessness and everything to do with duration.
The portal widened.
The person who came through was seventeen, or looked it: tall in the angular, recent way of someone who has grown fast and hasn't quite calibrated to it yet, with Riku's features and something behind them that was doing what Riku's face was sometimes trying to do and not quite managing — being completely present, completely open, without the armor of performed indifference.
He came through the portal and stopped.
He looked at the family assembled in the white space and did the thing people do in dream logic and impossible situations and occasionally very real ones: he verified the count. Four people. His father, his mother, his sister, and himself, standing two meters to his left, staring at him with a face he had presumably seen in mirrors but apparently found very strange to look at from this angle.
"Okay," the new boy said. His voice was steadier than it probably should have been. "Okay. This is —" He looked at Riku. "This is very strange."
"Who are you?" Kenji asked. He did not ask it harshly — he asked it the way he asked all questions that required accurate answers: with precision and without softening.
"My name is Riku Tanaka." A pause. "Also."
"From which timeline?"
"From —" He stopped. Started again. "From a branch. A different branch. One that diverged from yours approximately —" He calculated, or seemed to; his eyes did the thing Kenji recognized as the active-processing look. "Approximately two years ago. In my timeline, Dad found the frequency earlier. By a year. We went through the portals differently. Our trials were — shorter, I think. We came through the nexus and reached the destination timeline, and I —"
He stopped.
"What happened?" Aiko said. Her voice was careful, in the way that careful voices are when they're trying not to lead a witness toward a particular answer.
"On the other side. In the new world." He looked at his father with the specific, calibrated look of a person about to say something they have thought about many times and still haven't found a comfortable way to hold. "My dad — your version of me, in the other timeline — he's gone. He died. Eight months ago. Seismic survey accident, completely separate from the earthquake, completely ordinary and completely — gone." A pause. "And the system. When he died, the system lost someone who knew how it worked. The expansion he'd started — the second transit point, the Sumida River window — it wasn't finished. And without someone who could —"
"Finish it," Kenji said.
"Yes. Without someone who knew the full architecture. It stalled." The other-Riku looked at his father with the eyes of a boy who has spent eight months missing a specific person and has found, impossibly, that specific person in an impossible space. "I've been studying it. Everything he left. I've gotten as far as I can but there are parts I don't have the engineering background for and —" He looked at Kenji. "You do."
The nexus held them all in its thinning white.
Eight minutes on the timer. No, Kenji thought — the voice had said nine and they'd been talking for some of them. Seven, perhaps. Six.
He looked at his son — the one he'd raised, standing to his left, watching the other version of himself with the complicated expression of someone who has just been shown what their future contained the capacity for.
He looked at the other Riku — the one who had come through a portal that shouldn't have existed, from a divergent branch, looking for the man who died before he could finish his work.
He looked at Aiko, who was watching him with the look that meant: I see what you're thinking. And: we will talk about it. And: I trust you.
He looked at Hana, who had the small girl and the small boy on either side of her — Mei and whatever the boy's name was, both of them watching the situation with the patient old eyes of people who have seen enough impossible things to have stopped requiring the impossible to make sense before they could engage with it.
"The fifth signal," he said to the nexus. "When did it register?"
"When the second anchor came online," the nexus said. "The stabilization created a resonance window that allowed a cross-branch signal to reach us. The signal was already at the boundary — it had been attempting to reach this nexus for some time."
"He's been looking for this nexus," Kenji said.
"Yes."
"And if Dr. Saito hadn't come online when she did, the window wouldn't have opened and he couldn't have —"
"No."
He thought about the chain of it: Tomoko finding the frequency, following the train, walking through the open door; Dr. Saito in the station, her red notebook and her geochemical data; the second anchor coming online; the stabilization window opening; the fifth signal finding its way through. None of it planned. All of it consequential. The way good engineering worked and the way the world worked and the way love worked, actually, if you thought about it: not designed in its details but created in its structure, and then the details found their own way through the structure toward the thing that needed doing.
"The final portal," he said. "The destination timeline. It's not opening."
"It requires five member authorization now. The system has identified five members of the Tanaka family in this nexus. All five must authorize the transit together."
"He's not —" Riku, the original, said. He was looking at his counterpart. "He's from a different timeline. He's not part of our family."
The other-Riku looked at him. Something moved between them — that specific, uncomfortable electricity of two versions of the same person occupying the same space, each one a reminder to the other of what they are and what they could be and what they chose.
"The system identified a related resonance," the nexus said. "The relationship is non-standard but the bond is real. The decision of whether to include him in the transit is yours."
"What happens to him if we don't?" Hana asked.
"He returns to his branch. Which was his last known location before he crossed to reach this nexus."
"A world where your dad died," Hana said, to her counterpart across the space. "And the system is unfinished."
The other-Riku met her eyes. Something passed between them that siblings from any timeline would have recognized: the wordless communication that exists between people who have been in the same impossible situations and know exactly what the other one knows.
"He's trying to finish what Dad started," Hana said. She said it to the room, to all of them, with the certainty of someone who has found the true shape of a thing and is naming it. "That's why he came. Not to be rescued. To finish the work."
Kenji looked at the other-Riku and thought: yes. That's exactly it. I can see it.
He thought: a boy from a world where I didn't survive came looking for the knowledge I left behind because the work was unfinished and he decided that wasn't acceptable. That is — that is exactly who Riku would be. Who my son is. In any branch.
Five minutes. Maybe four.
He looked at his wife.
She was already looking at him. She nodded: once, small, the specific nod that meant yes without needing the word.
He looked at Hana. She was already nodding.
He looked at his Riku, who was looking at his counterpart with an expression that was complicated and raw and working through something in real time — the specific experience of looking at a version of yourself that has lived through something you haven't, and choosing whether that changes anything about how you see yourself, or others, or what you're willing to do.
His Riku said: "Yeah. Okay."
Kenji looked at the other-Riku.
"There's engineering to finish," he said.
"I know," the other-Riku said. "I've been trying to get to you for eight months."
"Then let's not waste the remaining minutes."
He looked at the nexus. "All five are present and consenting. Open the final portal."
The nexus spoke: "Final portal opening."
And ahead of them, in the white space, the destination bloomed: not blue-white this time but something warmer, something amber and ordinary and full of the specific sound of a city going about its business, fourteen million people and their ordinary Tuesdays, their coffee machines and their crowded trains and their cats on the street and their arguments about traffic and their children going to school and their total, beautiful, oblivious ignorance of what was building beneath them.
Tokyo. Safe. Waiting.
Kenji Tanaka stood in the nexus with his family — all five of them, by whatever definition the system was using, which he had decided was the correct one — and looked at the destination.
"Three minutes," the nexus said.
"We go together," Aiko said. Not a question.
— ✦ —
"We go together," he confirmed. They moved. Five people toward the amber portal, the ordinary sound of a saved city growing louder as they approached, and then Kenji stopped. "Wait." He turned. In the white of the nexus, thinning now at the edges, the field barely holding, two presences he hadn't thought about in the urgency of the last four minutes: Mei, the girl who had been in the forest for thirty-one subjective years in an eleven-year-old body. And the boy who had come through the second new portal — the one the other-Riku's arrival had opened — who had not yet told them his name. Both of them standing in the white space with the patient eyes of people who have been in impossible situations long enough to have a practiced relationship with waiting. "The system identified five Tanaka family members," Kenji said to the nexus. "What authorization is required for non-family transit?" A pause. "Non-family members may transit only if a family member sponsors the additional signal." "I sponsor," Hana said immediately. Her voice was clear and certain, the voice of someone who had figured out what she believed in a holographic forest and was not going to pretend she hadn't. She looked at Mei and the boy. "Both of you. I sponsor both." "Hana —" Kenji began. "The system said a family member can sponsor. I'm a family member." She looked at her father with thirteen-year-old eyes that had seen too much and were going to do something about it. "I know you're going to say the capacity is strained. I know there's a risk. I'm asking the nexus if it's possible." A long pulse from the nexus field. "At current capacity, with two anchors online and the transit window active: possible. Strained. But possible." Two minutes. Kenji looked at his daughter. He thought of himself at his laptop three weeks ago, hovering over YES with a weight he couldn't fully see. He thought of Dr. Saito in the station, saying: let me do this while there's time. He thought of the other Aiko on the bridge, saying: I've been holding things together for long enough. There were moments, he had learned, when you stopped calculating and started trusting. Not blind trust — informed trust. The trust that comes after you have done all the work you can do and the remaining variable is the human being in front of you. He looked at his daughter. She looked back. "Okay," he said. "We go together. All of us. Now." They ran.