They went back to the records room the next Sunday, this time with a narrower question.
Not who is she, but what is she.
The librarian, an older woman named Sato who had grown curious enough about their visits to stop pretending otherwise, pulled a thin, brittle folder from a locked cabinet without being asked. "You two are looking for the same thing everyone who's ever come in here quietly asking questions has looked for," she said. "There's an old scholar's journal. Local eccentric, decades back. Kept notes on the sightings nobody else took seriously."
The journal was handwritten, the ink faded to the color of weak tea, the pages soft with age. Hiroto and Yuki read it together at the back table, heads bent close over the same page, Yuki turning each leaf with careful fingers.
Most of it was rambling — half folklore, half the private theorizing of a man with too much time and too much rain. But one passage, near the middle, had been underlined twice by whoever wrote it, hard enough that the pen had almost torn the paper.
We live inside three directions, and time carries us through a fourth whether we consent to it or not. But I believe she does not live inside our directions at all. I believe she exists somewhere beyond them — a fifth place, folded so close to ours that it touches us only where the world grows thin. And the world grows thinnest in the rain.
The rain is not her prison. It is her doorway. It is the only place our world grows soft enough for her to press through it.
Yuki read it twice, her lips moving faintly over the words.
"That's why it's only ever rain," she said slowly. "Not fog. Not snow, unless the snow turns to rain first. Only rain. It's not weather to her. It's a door."
"And when the rain stops falling normally," Hiroto said, thinking of the way each drop had hung motionless in the air, "that's not her stopping time. That's her holding the door open long enough to actually step through it."
"Which would explain the cost," Yuki said quietly. "Holding a door open against everything it wants to do naturally probably isn't free. Not for her. Maybe not for the people standing near it, either."
Hiroto thought of Hokkaido — the missing hours, the stranger's eyes in his own mirror — and said nothing, because he didn't need to. Yuki already knew.
They stayed until the library closed, copying what they could by hand since the folder wasn't allowed to leave the building. Outside, the evening had turned the sky the color of wet stone, rain falling steady and unremarkable, obeying every ordinary rule it was supposed to.
"If she's not from here," Hiroto said as they walked, "not from this — not our directions, not our time — then how does she remember anything at all? How does she know your street, my mother, the river?"
"Maybe memory doesn't need the same directions we do," Yuki said. "Maybe it's the one thing that can cross over cleanly, even if she can't."
"And her own memory?"
Yuki considered this for a long moment before answering.
"Maybe that's the one thing that has to stay behind," she said. "On our side. Somewhere she's actually been standing — actually, physically, in this world, even for a second. Not just watching us from wherever the rest of her lives."
Hiroto stopped walking.
"Every place she's been seen," he said. "The station. Shirotani. Your street, two years ago. The shrine before it burned. Maybe those aren't just sightings. Maybe those are the only places she's ever actually arrived — even partway."
"So the piece of herself she's missing," Yuki said, catching up to the thought at the same speed he was having it, "isn't floating around in her fifth place at all. It's here. In ours. Left behind at whichever one of those spots actually mattered."
They looked at each other under the rain, both of them arriving at the same edge of the same idea.
"Your street," Hiroto said. "Where you grew up. We haven't gone there yet."
Yuki was quiet for a moment. It was, Hiroto realized, the first time he'd asked her to go back to the place her sister had died.
"I haven't been back since the funeral," she admitted.
"You don't have to—"
"I know." She started walking again, decisive now, the hesitation folded away and put somewhere he couldn't see. "But if there's a piece of her waiting there, I'd rather be the one who finds it than let it sit there another two years."
Hiroto fell into step beside her.
"Next week," she said. "After the Friday shift. We'll take the early train."
The rain kept falling around them, ordinary and patient, obeying its own rules and hiding, somewhere inside them, a door neither of them could see yet — but both of them, for the first time, knew exactly where to start looking for.