The mirrored pavilion “null²” (pronounced “null null”) drew around 600,000 visitors at Expo 2025 Osaka, Kansai (about 540,000 by the GREEN×EXPO Association’s count). One year after the Expo closed, on 14 October 2026, it reopens as “null²ⁿ (Null Null Nexus),” a permanent theatre on the fifth floor of Yokohama Landmark Plaza. And when GREEN×EXPO 2027, the Yokohama horticultural expo, opens on 19 March 2027, its venue will hold “null⁴ (Tetra Null),” an outdoor work of four rotating mirrored structures.
Producer Yoichi Ochiai calls the two projects a “reincarnation” of null², not a relocation. What carries over and what changes? We read the announcements by Sustainable Pavilion 2025 Inc. and the GREEN×EXPO Association (the Japan Association for the 2027 International Horticultural Expo), the two official sites and Ochiai’s own posts on note. Figures and dates are as announced on 13 September 2026.
What null² was
null² was a signature pavilion at Expo 2025 (13 April to 13 October 2025), produced by Ochiai. The organisers describe it as an experiential installation built on the Buddhist idea of emptiness and the computing term “null,” using a special mirror film, LEDs and robotics. Its mirrored outer wall reflected the surroundings while rippling and deforming, and inside, visitors met a digitised double of themselves called a “Mirrored Body.”
About 600,000 people visited during the Expo according to the operator, Sustainable Pavilion 2025 Inc.; the GREEN×EXPO Association’s page on null⁴ puts it at about 540,000 from Japan and abroad (the difference in counting is not explained). The Mirrored Body app, which creates that double, was used by 170,000 people. The pavilion won first place in Casa BRUTUS’s “Best Pavilion 20,” the grand prize of the Minna no Kenchiku Awards 2026 (13,750 public votes) and a silver prize at the JCD/DSA Japan Space Design Awards. The crowdfunding campaign launched after closing, “Nurunuru no Ohikkoshi” (the null² move, on READYFOR from 1 October to 19 December 2025), passed 100 million yen within 23 hours and ended with about 281.5 million yen from 15,821 backers. Backers learned that the Yokohama Expo would be the destination from an update posted on that page on 17 December 2025, before the official announcement.
Two sequels
The announcement of 7 April 2026 split null²’s future in two.
| null²ⁿ (Null Null Nexus) | null⁴ (Tetra Null) | |
|---|---|---|
| Where | Yokohama Landmark Plaza, 5th floor (Minato Mirai) | SATOYAMA Village inside the GREEN×EXPO 2027 venue |
| When | Opens 14 October 2026, permanent | 19 March to 26 September 2027 (the Expo period) |
| What | Indoor permanent theatre. Five rooms including two LED theatres, about 60 minutes | Outdoor sculpture. Four rotating mirrored structures and a giant rotating object likened to a prayer wheel |
| Who | Sustainable Pavilion 2025 Inc. (organiser) | Digital Nature and Arts, a general incorporated association (planning) |
| Tickets | Timed entry only. On sale since 14 July 2026 | Inside the venue. How it will be viewed has not been announced |
null²ⁿ: the experience, not the building, made permanent
null²ⁿ does not rebuild the Osaka pavilion. It rebuilds what happened inside it as a permanent theatre. The Osaka pavilion had one LED theatre; Yokohama will have two. Visitors move through five rooms in about 60 minutes. In August 2026 the organisers revealed the concept of a third room with no video at all, a “sound-only room.” Mirrored spaces reflect sound as well as light and are poor for precise listening, so the new room is an anechoic space with many speakers that let you feel where sounds are and how they move. Ochiai compared the LED theatre to a sauna and the silent room after it to the cold plunge.
The “ⁿ” stands for nexus. The facility is meant to be a permanent meeting point for people, experiences and places, with regular events and a visitor community planned. Four parties announced it together: Sustainable Pavilion 2025, Digital Nature and Arts, Mitsubishi Estate (which runs Yokohama Landmark Tower) and Macnica (which co-developed the Mirrored Body platform). Access, prices and what to know on the day are in our visitor guide to null²ⁿ.
null⁴: four mirrors turning in the open air
null⁴ is described as a “landscape-transforming sculpture” for SATOYAMA Village at the Expo venue. Four mirrored structures rotate while reflecting the surroundings, taking in the flowerbeds, the sky, the wind and visitors’ shadows. A giant rotating object likened to a prayer wheel moves with them, and the work looks different by day, at night and across the seasons. The “⁴” (tetra) refers to the four structures and to the tetralemma, a logic that holds four positions at once. The GREEN×EXPO Association’s own website also has a page on null⁴, presenting it as a mirrored living sculpture in SATOYAMA Village that rotates while reflecting flowers, sky and visitors.
The official site positions the work as “not an extension of a pavilion but a Landscape-Transforming Sculpture placed within nature,” changing how the landscape is seen through reflection and rotation alone, without touching the site itself. The visitor instructions for the interior are listed as “still in development,” so as of September 2026 they are unannounced. The GREEN×EXPO Association and Digital Nature and Arts are recruiting partners for funding and for services such as video, sound, planting and operations.
Mirrored Body ties them together
The link between the two sites is the Mirrored Body app that 170,000 people used in Osaka. A full-body scan creates your digital double, and that double reacts to the shows at null²ⁿ and null⁴. The organisers say visitors who made a double in Osaka will meet it again in Yokohama. The null²ⁿ site says the app is not required, but installing it brings priority booking and extra effects. A “Mirrored Body Lite” is available for children aged 13 and under and for people living outside Japan.
In Ochiai’s own words
The following are Ochiai’s own words, chosen and quoted briefly by us from his comment in the announcements and from the free sections of his posts on note. Our translations from the Japanese are in brackets.
In his comment attached to the 14 July 2026 announcement, Ochiai wrote of the Expo’s closing: 「万博は閉じた．しかし計算機自然の森は閉じない．」 [The Expo has closed. But the forest of computational nature does not close.] He continued that null² gave up its mass in Osaka and regains it in Yokohama, listed the moves from Osaka to Yokohama, from festival to permanence, from city to forest, and ended with 「おかえり，ヌルの森．」 [Welcome back, Forest of Null.] That last line also opens the null⁴ official site.
On the name, his note post of 19 March 2026 says 「null²のままだとあまり味がないし」 [keeping it as null² would be a bit bland], and explains that since the form was changing fundamentally, he wanted a name that stood for that. His post on the announcement day, 7 April, says 「null²の遺伝子は受け継がれて続いていく」 [the genes of null² are passed on and continue], followed by a remark that it really did move to a forest. The same post mentions how happy he felt surrounded by Tunku Tunku and Myaku-Myaku at the launch.
Speaking at an Expo legacy event in Osaka on 23 August 2026, he said that an Expo’s legacy is not only the buildings and exhibits that get preserved. The tens of thousands of Expo fans who keep the culture going after closing are a legacy in themselves. He also described null²ⁿ as an experience centred on theatres and null⁴ as sculptural architecture merged with nature, and said the two connect as one story when you experience both.
Miraikan’s exhibit is a separate thread
Ochiai’s work is not confined to Yokohama. Miraikan, the National Museum of Emerging Science and Innovation in Odaiba, Tokyo, has had his permanent exhibit “Computational Nature” since November 2019. It was partly renewed on 1 April 2026. Miraikan calls the renewal its “second Expo 2025 project” and added a work that applies the AI techniques used in null², plus a new piece in which an AI answers a telephone in Ochiai’s voice. It is a separate project from null²ⁿ and null⁴, but it is a permanent place in Tokyo to see the same “digital nature” idea.
Note that Miraikan closes for building works from 1 October 2026 to 22 April 2027. Our Japanese-language article on the exhibit has the details.
Our take
If you want to see the null² building again, the thing to know first is that what comes to Yokohama is the experience and the idea, not the building. null²ⁿ is an indoor theatre. null⁴ is an outdoor sculpture. The mirrored building from Osaka is at neither.
For rail travellers, the two are far apart even though both are in Yokohama. null²ⁿ is in Minato Mirai; null⁴ is at the venue in Seya. To do both in one day during the Expo, the practical order is the venue in the morning and Minato Mirai in the late afternoon. null²ⁿ plans to stay open until 21:00, so leaving the venue early still leaves time.
As of September 2026 the contents of null⁴ are “in development.” We will add the visitor instructions and whether booking is needed when they are announced.
Come here from what carries over from Expo 2025, and go on to the visitor guide to null²ⁿ.