Myogi Castle




Myōgijō was founded by the Mimura Clan. Along with Takeijō, another major stronghold of theirs, it provided a commanding view of the Matsumoto Basin, but was somewhat blind to traffic coming from the Kiso Valley. During the Sengoku period the Mimura supported the Ogasawara Clan but switched allegiances during the Battle of Shiojiri Pass in 1548, which Myōgijō was very near to, contributing to the destruction of their former overlords. From 1550 the Mimura came under the sway of Takeda Shingen. It seems Takeda didn’t trust them, however. In 1555 when clan boss Nagachika and his retinue were staying over at a temple in Kōfu in the New Year, Takeda sent in one of his commanders to assault them in a surprise attack. Nagachika and 213 of his men were wiped out. It is not known why Takeda ordered the slaughter of the Mimura, but one theory is that he viewed their previous treachery (against the Ogasawara) as a liability and didn’t want to give them a chance to rebel against him at a crucial moment like they had done against the Ogasawara. When news reached Myōgijō of the massacre there was uproar. The remnants of the clan attempted some sort of revenge scheme against Takeda, attacking him at Fukashijō (the castle which later became Matsumoto Castle), but this failed and the clan was wiped out. Myōgijō was abandoned around 1590. Although there are no structures left, a shrine, Myōgi-jinja, located in the castle’s central bailey has been maintained to this day. The village of Seba developed first at the base of Mt. Myōgi as a settlement supporting the castle. Later it was built up to the south as Seba-juku, a station on the Nakasendō, in the area that the current train station is located today. I noticed that some homes lining the street near to the site are narrower compared to more spacious rural homesteads in the surrounding countryside, which is a small clue as to the former village center being located there.

Visit Notes

Myōgijō (also called Myōgisanjō) was a medieval mountain citadel used by the Mimura Clan alongside their fortified manor house at the foot of the mountain. The main residence was the manor house but in times of trouble the fortified mountain was a safe place to retreat to. At that time there were many such mountaintop fortresses used in conjunction with fortified residences (called Yakata or sometimes Bukeyashiki). The ruin consists of the central bailey situated on a flattened area at the top of the mountain and a secondary bailey slightly below that. Unusually large trenches, at least for a site of this size, surround these baileys, cutting deep into the mountainside. Striping the mountain ridges are also the deformed remains of tatebori (climbing trenches). According to a sign at the site, these earthworks are called Ōtatebori and Ōhorikiri. The site can be accessed by either taking a trail from Chōkōji or from Kamai’an, a cottage built by an artisan-hermit in 1783 and subsequently used as a school to educate commoners. It is on the site of the former yakata (Kamaian Yakata). At the foot of the mountain there is an embankment overlooking terraced paddies. Although there is a torii gateway here it is not the start of the trail: that can be found to the right, past the Seba Village Museum. Information about the castle and the Mimura Clan is presented in the museum.


Castle Profile
English Name Myogi Castle
Japanese Name 妙義城
Alternate Names Myōgisanjō
Founder Mimura Clan
Year Founded Sengoku Period
Castle Type Mountaintop
Castle Condition Ruins only
Historical Period Pre Edo Period
Artifacts Ōtatebori, Ōhorikiri, horikiri, kuruwa, tatebori
Features trenches
Visitor Information
Access Nearest station is Seba Station on the Chuo Line
Visitor Information 24/7 free; museum is 10am to 5pm on weekends only
Time Required two hours
Location Shiojiri, Nagano Prefecture
Coordinates 36° 6' 29.12" N, 137° 54' 27.11" E
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Added to Jcastle 2019
Contributor ART
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