Tsuyama Castle (Kakuzan Castle)

Tsuyama Castle, a Castle of Mimasaka: The Founding of Tsuyama Castle and the Mori Clan

Tsuyama Castle (also known as Kakuzan Castle) is a masterwork of early modern castle architecture, built over more than a dozen years from its inception in Keicho 8 (1603) to Genna 2 (1616) by Mori Tadamasa, a senior retainer of the Tokugawa, in Mimasaka Province (present-day Tsuyama City, Okayama Prefecture). The Mori clan was a daimyo family of the Chubu region, and Tadamasa's elder brother Ranmaru (Mori Naritoshi) is renowned as a page of Oda Nobunaga who fell alongside his lord in the Honnō-ji Incident. After Nobunaga's death, Tadamasa entered the service of Tokugawa Ieyasu and was granted Mimasaka Province (186,500 koku) for his service at Sekigahara, where he built Tsuyama Castle.

The castle layout occupies the north bank of the Yoshii River, centered on the summit of Mt. Kakuzan (approximately 66m), with the honmaru, ninomaru, sannomaru, and obi-no-maru arranged in terraced fashion. At its completion, it possessed a magnificent five-story, six-floor tower and ranked as one of the largest castles in the Chūgoku region. However, following the Abolishment of Domains and Castles Edict (1873), all structures were dismantled, and today only the stone walls of each kuruwa remain.

A Castle of Stone Walls: One of Japan's Three Great Mountain Castles

Tsuyama Castle's greatest attraction is its magnificent stone walls. The stone walls supporting the complex layout atop the mountain employ diverse techniques—high stone walls, nozura-zumi (rubble work), and sangi-zumi (quoin corners)—representing the pinnacle of beauty in early modern castle masonry. Renowned as a "castle of stone walls," it stands alongside Okayama's Kōrakuen and Kurashiki's Bikan District as one of Okayama Prefecture's premier attractions.

In spring cherry blossom season (early April), approximately 1,000 Sōmei Yoshino trees within the castle grounds reach full bloom, and the interplay of stone walls and cherry blossoms is widely known throughout Japan as one of its finest flower-viewing sites. It has been selected as one of the "100 Famous Cherry Blossom Sites of Japan," and many tourists visit during this season. A combined visit with the nearby Tsuyama Railway Museum is also popular.

From the Mori to the Matsudaira: Tsuyama Domain and Sword Culture

The Mori clan ended without an heir in 1697 under the third lord Nagatsugu, and the Echizen Matsudaira family (Matsudaira Nobutomi) was installed at Tsuyama Domain with 100,000 koku. The Matsudaira family thereafter governed Tsuyama Domain until the end of the Edo period as a shinpan (related) daimyo family with close ties to the shogunal house.

The Tsuyama Domain under Matsudaira rule (18th–19th centuries) is known as a culturally flourishing domain where both Confucian and Dutch learning thrived. In particular, the Dutch studies scholar Udagawa Genzui (1756–1798), a native of Tsuyama Domain, is renowned as a pioneer in introducing Dutch medicine to Japan, and his successors formed what became known as "Tsuyama Dutch Studies." This intellectual culture's interest extended to sword appreciation, and the Matsudaira formed a collection of high-quality swords.

Bizen Sword Distribution Hub: Mimasaka's Deep Connection to Swords

The most important intersection between Tsuyama Castle and sword culture lies in Mimasaka's geographical position. Mimasaka is located north of Bizen Province (southern Okayama), and had extremely deep ties with Bizen, which was home to Osafune, a major center of Bizen sword production. Osafune, located in Nagaoka-chō, Setouchi City along the JR Akō Line, was where the largest community of swordsmiths in Japan concentrated from the Kamakura through Sengoku periods.

Mimasaka warriors favored Bizen swords, and samurai in the Tsuyama castle town wore blades of the Osafune school. Works by swordsmiths of the Osafune school—Mitsutada, Nagamitsu, Kagemitsu, Kanemitsu, and Sukesada—flowed from Bizen into Mimasaka, enriching the martial culture of the region. The Mori clan, lords of Tsuyama Castle, were also major patrons and purchasers of Bizen swords. Mori Ranmaru (Mori Naritoshi) is known as Nobunaga's most beloved page, and his interest in swords was likely deeply influenced by Nobunaga; it is probable that Ranmaru possessed fine blades including works from Bizen.

Furthermore, Mimasaka, as a neighboring province of Bizen, was positioned on sword distribution routes, serving as a way station through which Bizen blades flowed via the Sanyōdō and Sanyindō routes to consumers across Japan. In this sense, Tsuyama functioned as a "gateway to Bizen swords."

Tsuyama Castle Today: Stone Walls and Cherry Blossom Sanctuary

Today the Tsuyama Castle ruins (Kakuzan Park) are a renowned site attracting visitors from across Japan as a destination famous for its stone walls and cherry blossoms. Sometimes cited alongside Bitchū Matsuyama Castle and Takeda Castle as "one of the three great mountain castle stone walls of Japan," its magnificent masonry consistently captivates castle enthusiasts.

The "Bitchū Yagura (Reconstructed)," restored in 2005 and rebuilt within the castle grounds, serves as an exhibition facility conveying the castle's internal structure and period life. The Tsuyama Local History Museum in Tsuyama displays swords, weapons, and artwork associated with the Mori and Matsudaira families.

A combined tour of Tsuyama's railway and sword heritage—Tsuyama Castle (stone walls and cherry blossoms), Tsuyama Railway Museum, and the Bizen Osafune Sword Museum (approximately one hour by car)—offers a rich exploration of the Chūgoku region's martial and railway culture.