The Former Mitsui Bunko Second Library: A Hidden Concrete Treasure in Tokyo's Shinagawa
Tucked away in the leafy Bunko-no-Mori Park in Shinagawa Ward stands a small but quietly remarkable structure: the Former Mitsui Bunko Second Library (Kyū Mitsui Bunko Daini Shoko). Completed in 1922 during the Taishō era, this modest three-story building is regarded as one of the oldest surviving examples of wall-bearing reinforced concrete construction in Japan. Designated as a Registered National Tangible Cultural Property in April 2020, it offers visitors a rare glimpse into the early history of modern Japanese architecture, the rise of the powerful Mitsui family, and the careful craft of preserving precious historical documents.
A Quiet Survivor in the Heart of Shinagawa
The Former Mitsui Bunko Second Library is the last remaining original building from what was once the Mitsui Bunko archive complex. The land it stands on has its own layered history. During the Edo period, the area served as the lower residence (shimoyashiki) of the Hosokawa clan, lords of the Higo Kumamoto domain. In 1890, the Mitsui family, one of Japan's most influential financial dynasties, acquired the property. By 1918, the family had relocated their editorial office from Nihonbashi to this site to establish the Mitsui Bunko, a private archive devoted to managing and preserving the family's vast collection of historical documents.
Originally, the complex featured an administrative building and two library buildings. After the dissolution of the Mitsui zaibatsu following World War II, the site was sold in 1951 and later became home to the National Institute of Japanese Literature, where the Second Library continued to serve scholars and researchers for decades. When the institute relocated in 2008, the surrounding land was transformed by Shinagawa Ward into a disaster-prevention park, which opened as Bunko-no-Mori in 2013. The Second Library was carefully preserved as a cherished landmark and namesake of the new park.
Why This Small Building Earned National Recognition
At first glance, the building's modest rectangular footprint of roughly 14 by 9 meters might not suggest national significance. Its true value, however, lies in what is hidden within its walls. The Second Library was constructed using a wall-bearing reinforced concrete method, in which the load of the structure is supported not by columns but by the walls themselves. This technique was unusual for its time in Japan, and the building is widely considered one of the oldest surviving examples of this method in the country.
The choice of construction was deliberate and ingenious. By eliminating internal columns, the architects could maximize the open interior space available for shelving, while the thick reinforced concrete walls offered exceptional protection against fire, a constant threat to paper-based archives. The slabs forming the floors of each story and the third-floor ceiling are also made of reinforced concrete, creating a robust, fire-resistant shell. Inside, steel columns supporting the bookshelves were cleverly designed to also help bear part of the structural load, demonstrating a level of engineering sophistication that earned high praise from cultural property experts. The combination of structural innovation, fire-conscious design, and meticulous craftsmanship made it a natural candidate for the national register.
Architectural Highlights and Hidden Details
One of the most charming and clever features of the Former Mitsui Bunko Second Library is its exterior finish. What appears at a glance to be a tiled facade is in fact mortar painstakingly worked to imitate the look of tiles. The joints between the imitation tiles use a technique called fukurin-meji, the same elegant raised-rim jointing seen on the brickwork of Tokyo Station. This subtle craftsmanship reflects the high standards of Taishō-era artisans, who blended modern materials with traditional aesthetic sensibilities.
Another fascinating story is etched into the building's windows. Although the structure was already designed with fire protection in mind, the devastating Great Kantō Earthquake of 1923, which struck just one year after completion, prompted further safety upgrades. Many windows were half-filled with mortar, leaving a distinctive checkerboard pattern still visible from outside today. These modifications speak to the seriousness with which the Mitsui family approached the preservation of their archives, and they have since become one of the building's most distinctive visual signatures.
Visitor Information and How to Enjoy the Site
For safety reasons, the interior of the building is generally closed to the public, and today it serves a practical second life as a disaster-prevention storage facility for Shinagawa Ward. Visitors can, however, walk right up to the perimeter fence within Bunko-no-Mori park and admire the exterior at any time during park hours. The combination of the imitation tile walls, the checkerboard windows, and the soft greenery surrounding the building makes for memorable photographs, especially in spring when cherry blossoms bloom and in autumn when the surrounding trees turn shades of gold and crimson.
If you wish to see the inside, plan your visit around early November, when Shinagawa Ward holds its annual Cultural Property Open Days (Bunkazai Ippan Kōkai). On these special days, the building is opened to the public, often accompanied by guided commentary from a curator. Dates are announced each year on the Shinagawa Tourism Association website, so checking ahead is recommended.
Exploring the Neighborhood
A visit to the Former Mitsui Bunko Second Library pairs beautifully with a wider stroll through this delightful corner of Tokyo. The library sits within Bunko-no-Mori, a tranquil green space that connects to the adjacent Togoshi Park (Togoshi Kōen), a traditional Japanese-style garden originally part of the same Hosokawa estate. Together, the two parks form a peaceful oasis perfect for a relaxed afternoon walk.
Just a short walk away lies Togoshi Ginza, one of Tokyo's most famous and longest shopping streets. Stretching for roughly 1.3 kilometers, it is lined with hundreds of small shops, casual eateries, and beloved street-food stalls offering everything from croquettes to sweets. The atmosphere is wonderfully local and friendly, providing a vivid contrast to the quiet historical air of Bunko-no-Mori. For those interested in further exploring the Mitsui legacy, the Mitsui Memorial Museum in central Nihonbashi houses a remarkable collection of art and artifacts from the Mitsui family and offers another perspective on the family's cultural impact across the centuries.
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Q&A
- Can visitors enter the building?
- In general, the interior is not open to the public for safety reasons. However, special openings are typically held during Shinagawa Ward's Cultural Property Open Days in early November each year, when the building can be viewed from inside with guided commentary.
- When was the Former Mitsui Bunko Second Library built?
- It was completed in 1922, during the eleventh year of the Taishō era. Remarkably, it survived the Great Kantō Earthquake the very next year and continues to stand more than a century later.
- Why is this building so historically significant?
- It is recognized as one of the oldest surviving examples of wall-bearing reinforced concrete construction in Japan, a pioneering structural method at the time. It also demonstrates exceptional craftsmanship and a thoughtful approach to fire protection and document preservation.
- How do I get to Bunko-no-Mori Park?
- The most convenient route is via the Tokyu Oimachi Line to Togoshi-koen Station, from which it is about a two-minute walk. The Toei Asakusa Line's Togoshi Station is also nearby, about a nine-minute walk away.
- Is there an admission fee?
- No. Bunko-no-Mori is a public park, free to enter, and the exterior of the Former Mitsui Bunko Second Library can be viewed at any time during park opening hours at no charge.
Basic Information
| Name | Former Mitsui Bunko Second Library (Kyū Mitsui Bunko Daini Shoko) |
|---|---|
| Designation | Registered National Tangible Cultural Property (Building) |
| Registration Date | April 3, 2020 |
| Year of Completion | 1922 (Taishō 11) |
| Structure | Three-story reinforced concrete (wall-bearing structure), metal sheet roof, building area approximately 130 square meters |
| Location | 1131-1 Yutaka-cho 1-chome, Shinagawa-ku, Tokyo (within Bunko-no-Mori Park) |
| Owner | Shinagawa Ward |
| Access | About 2 minutes on foot from Togoshi-koen Station (Tokyu Oimachi Line); about 9 minutes from Togoshi Station (Toei Asakusa Line) |
| Admission | Free (exterior viewing only; interior open during special events) |
References
- Former Mitsui Bunko Second Library Registered as National Tangible Cultural Property | Shinagawa Ward Official Website
- https://www.city.shinagawa.tokyo.jp/PC/sangyo/sangyo-bunkazai/20200925125031.html
- Former Mitsui Bunko Second Library | Cultural Heritage Online
- https://bunka.nii.ac.jp/heritages/detail/445143
- Bunko-no-Mori (Former Mitsui Bunko) | Shinagawa Tourism Association
- https://shinagawa-kanko.or.jp/spot/bunkonomori/
- Former Mitsui Bunko Second Library Registered as National Tangible Cultural Property | Mitsui Public Relations Committee
- https://www.mitsuipr.com/news/2019/1128-3/
Last verified: 2026.04.21