Shiroishi Castle (白石城, Shiroishi-jō), located in Shiroishi City, Miyagi Prefecture, is a historic Japanese castle built on a hill (a hirayamajiro, or hilltop-style castle). Also known as Masuoka Castle (Masuoka-jō), it is designated as a historic site by Shiroishi City and is listed as No. 105 in the Continued Top 100 Japanese Castles (続日本100名城). It stands as a major symbol of the region’s cultural and historical heritage.
The origins of Shiroishi Castle date back to the medieval period, when it served as the residence of the Shiroishi (or Katta) clan. During the late Sengoku period, the castle changed hands multiple times. In the Edo period, it came under the control of the Katakura clan, senior retainers of the Sendai Domain, and served as both a political and administrative center. Like Yatsushiro Castle in Kyushu and a few other exceptions, Shiroishi Castle was granted special permission to remain under the Tokugawa shogunate’s “One Castle per Province” (ikkoku ichijō) policy. It continued its role until the Meiji Restoration.
The castle structure evolved through the Edo period, gradually expanding in scale. Based on comparative analysis of historical maps from different eras, it eventually developed a six-enclosure, five-bailey layout:
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On the hilltop: Honmaru (main bailey), Ninomaru, Chūnōmaru, Nishikuruwa
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Middle slope: Numamaru, Minamimaru, Tatsumikuruwa, Obikuruwa, Umayakuruwa
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At the base: Sannomaru and Sotokuruwa
At the heart of the Honmaru stood a three-story yagura (tower), functioning in place of a tenshu (main keep). While some believe it was expanded from an earlier two-story structure, archaeological and historical sources (such as the report Excavation of Shiroishi Castle – The Castle of Katakura Kojūrō) indicate that it was built as a three-story tower from the beginning. Due to its status as a branch castle and political considerations under the shogunate, it was referred to as a “great turret” (ōyagura) rather than a “tenshu.”
The current three-story tower and gate were reconstructed in 1995 (Heisei 7), based on historical drawings and archaeological data to reflect the Edo-era appearance as closely as possible. Several original components are also preserved:
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Umayaguchi Gate was relocated to become the main gate of Enmei-ji Temple
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Higashiguchi Gate was moved to Tōshin-ji Temple
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Former buildings from the upper residence and inner quarters were preserved in Natori City and Shiroishi City
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Many earthen embankments remain in their original form, offering valuable insight into Edo-period castle construction techniques.
