Another skyline on the far side of the glass: Stable Window 1 and 'the Lit City' enter a third year — and this paper opens a Dimensional Survey section

Two kilometres off Haneda, at the top of a steel tower standing in the bay, there is a room about the size of twelve tatami mats. One wall is a single sheet of reinforced glass nine centimetres thick. Most of the time it shows nothing but the dark water of the bay. But when the Yuragi opens, the view beyond the glass changes without a sound.

On the evening of the 7th, forty minutes after this reporter entered the window room, it came. The sea surface trembled like a thin film, and in the next moment the night skyline of a city of stacked stone towers appeared. The tallest, we are told, correspond to thirty storeys. In countless windows burned an orange light that did not flicker — not electric light. One of the window keepers wrote the time on the log sheet with a practised hand: "17:52, open. Lineage 7, visibility good."

The idea of a stable window began with the "recurring Yuragi" confirmed off Haneda in 2021. A Yuragi normally opens with no warning as to when or where, and onto a different world line each time. But this one point off Haneda opened again and again, in the same place, onto very nearly the same world. The TDA created its Dimensional Survey Division in 2023 and installed a permanent observation rig — the "window rig" — at the site. Stable Window 1 entered service in March 2024.

The name "window" came naturally from the look of the thing. But the head of the division says it is closer to a telescope. "No light gets through from our side. No sound. Throw something and it drops in front of the glass. We can only see them. Three years on, that has not changed."

The one-way nature of the Yuragi holds for stable windows too. What changed is that the same world can now be watched continuously. Since the fragmentary observations of 1979, other world lines had been described through a few seconds of footage or a single drift object. Window 1 has accumulated more than 1,900 hours of continuous observation.

Lineage 7, provisionally named "the Lit City". The facts the division has confirmed in three years run to forty A4 pages in its published summary.

The city is built of stone; the tallest buildings are estimated at ninety metres. Streets are narrow and steep. The inhabitants look much like people here, dressed mostly in heavy cloth. At night, a resident places a hand in a recess in a wall, appears to read from a small tag, and an orange light comes on in the recess. The division provisionally calls the procedure a "formula". The same gesture has been recorded producing water and opening doors.

"The question of whether this is the source of exogenous technology naturally comes up," the division head says. "There are resemblances between what our licensed artificers do and the gestures of the 'formula' over there. But we do not conclude. Wanting to connect things that look alike is a wish, not an observation."

Residents usually show a tag resembling a licence before using a formula, and have been observed receiving such tags at gatherings that look like guilds. In having institutions, at least, the Lit City resembles this one.

More is unknown than known. There is no evidence that the far side is aware of ours. In three years a handful of residents have appeared to stop and "look at" the window, but the division treats these as probable reflections on the far side of the glass, not as evidence of recognition.

The writing cannot be read. More than 2,000 symbols from formula tags have been recorded; none has a meaning. The same is true of the language: the sound that reaches the window is fragmentary, and analysis has been entrusted to the 7th International Joint Study.

And the city's edges cannot be seen. The window's field of view is fixed; it shows the same block from the same angle. "Three years watching the same street through the same window. We do not know the name of their city, or of their country."

Window 1 has admitted the public since 2025 — eighty people a day, by lottery; in August the odds were 31 to one. It has entered the elementary-school field-trip circuit, and on the afternoon of the 7th thirty-eight sixth-graders from Sunamachi Third Elementary visited the window room.

The window did not open while the children were there. "Not opening is also an observation," a keeper explained, and one child asked whether that meant the other side had the day off. The room laughed. "Whether they have days off," the keeper said, straight-faced, "is also not yet known."

Five teacups stand in a row on the sill. The keepers take turns sitting before the window through the night. "Some days it opens for a few minutes; some days it stays open eight hours. It is a job of sitting and waiting. Like an observatory — tedium and a single instant, both," says a keeper of three years, 41.

Five stable windows are now in service: Window 1 off Haneda; Window 2 in the bay warehouse district (Lineage 19, "the Sea of Mechanisms"); Window 3 in the Inagi valley in West Tama (Lineage 88, "the Slime Marsh"); Window 4 on the Oji hill in the north (Lineage 63, "the Giant Plains"); and Window 5 in Kameido (Lineage 52, "the Sword Country"). The worlds they show are entirely unlike one another.

From today this paper opens a Dimensional Survey section, reporting daily on the worlds beyond the windows from the division's releases and from what our reporters see in the window rooms. We have settled on one rule: to write what is known and what is unknown separately, and not to load the far side with meaning. Even so, every time a window opens, we are told that the world is wider than we thought. That surprise we intend to pass on as it is.

On the night of the 7th, Window 1 closed at 19:24. It had been open for one hour and thirty-two minutes. The lights in the windows of the Lit City did not flicker once.