Nakasai Castle is thought to have been first built in 1221, perhaps by Naka Saburōzaemon as his residence. The Naka Clan were vassals of the Ônaka Clan. The castle, then under Naka Michitoki, was involved in the civil war of the Nanbokuchō Period, and in 1365 the Naka Clan, then under Naka Muneyasu, was relocated to Tamba, and the Satake Clan took over the area. It is perhaps the Satake Clan then which built up the castle as we see it today, clearly a Sengoku Period construction. It consisted of three principal baileys separated by moats, and an outer residential area.
The Satake sided with Toyotomi Hideyoshi in his campaign against the Hōjō at Odawarajō, which Nakasaijō likely played a part in, and became very powerful in Hitachi as a result. The Clan would side with Ishida Mitsunari at the Battle of Sekigahara, however, and be punished by the victorious Tokugawa Ieyasu by their removal to a small, isolated fief based around Kubotajō, Akita, in 1602. Nakasaijō was abandoned at this time.
The ruins of Nakasai Castle consist of earthworks such as tall dorui (earthen ramparts) and karabori (dry moats). It is classified as a hirayamajiro (hilltop castle) because it is built on a sloping clifftop, 30m tall. The moats also run between the clifftop and the ramparts of the main bailey, providing an extra line of defence in addition to the elevation itself. I noted this feature earlier at Chojayama Castle, and later at Urizura Castle too. By contrast, even though the Ina Valley in Nagano Prefecture has many clifftop castle sites, they relied soley on the terrain to protecte them from the cliffside.
The castle ruin is now the site of a temple, Hōdōin, which occupies the main bailey. The temple, however, consists of just a cemetary, main hall and priest's house, and there is still a lot of empty space, the inner precincts of the castle being quite vast. The dorui the whole way around the main bailey is well preserved, and there are what I think may be segments of dorui rising out of the surrounding countryside which previously constituted the castle's outer baileys. The size of the castle, known from historical maps, meant that it could be fairly called a small town. Viewed from satellite images, we can see that a large jutting promontory pushes from the mountainous interior in the direction of Mito and that Nakasaijō was located on its tip, with the Naka River to the north. This commanding position allowed the castle to lord over the surrounding plains.
|English Name||Nakasai Castle|
|Castle Condition||Ruins only|
|Designations||Prefectural Historic Site|
|Historical Period||Pre Edo Period|
|Artifacts||Karabori, Kuruwa,Yokobori, Dorui|
|Access||Hitachi-Kounosu Station on the Suigun Line; 90 minute walk|
|Visitor Information||24/7 free; temple|
|Time Required||60 mins|
|Location||Shirosato, Ibaraki Prefecture|
|Coordinates||36° 27' 27.32" N, 140° 24' 29.27" E|
|Year Visited||Viewer Contributed|
|Added to Jcastle||2020|