Ibarayamajō was a satellite fortification of Mikkaichibajō. The garrison commander is said to have been Sawando Kansuke. Kansuke is also said to have been a vassal of the Obinata Clan who were based at Iidajō to the northwest. The fort was already in place from at least the middle 16th century when it was captured in 1556 by Yamagata Masakage fighting for Takeda Shingen. See Mikkaichiba Castle for more information.
Ibarayamajō is a hilltop earthworks yamajiro (mountaintop castle) in the Kamishiro area of Hakuba Municipality. There are some ruins of the medieval castle, but also ruins which relate to before and after it, and where one story ends and another begins is not always easy to dissever. Ibarayamajō is thought to have been a satellite fort of Mikkaichibajō, and, from what remains, it's not hard to see Ibarayamajō as similar in layout to Mikkaichibajō.
Ibarayamajō appears to have been made up of integral baileys esconced by obikuruwa (belt baileys), and maybe karabori (dry moats). There are remnants of these trenches in the forest around the clearing to the right as one comes up the hill. To the left of the torii gateway there appears to be nothing, but if one goes over the embankment then below there is clearly a horikiri (trench) bisecting the ridge. Beneath the main bailey on the western side one can trace a narrow ledge, now covered in cedars, which goes all the way to the rear of the bailey space, the remnant of either a ringing moat or narrow ring bailey perhaps.
The earth at the rear of the main bailey is banked up wide enough to accomodate a small tower, and there is piled earth to the west of the main bailey. To be honest, it looks like these parts were modified with the construction of the shrine which was built in 1909 (the original shrine hall was destroyed in an earthquake in 2014, and now only a small kami house stands), as there's something off about them. To the rear of the main bailey is a depressed area.There is a path up from somewhere here working through a creek to the left, and to the right there is a solid earthen wall running north. This looks like dorui (earthen ramparts) but it's quite unusual in that it is attached to the embankment of the bailey above (a long earthen bridge then perhaps?). In this shaded area are two large, circular mounds: these are kofun (ancient tumuli) which predate the fort. They also show signs of being moated, whch was not unusual for kofun, even those built on hilltops. It's possible they also served some function at the medieval fort too, such as platforms for watch towers or smoke signals; they are considered to be within the footprint of the fort.
|English Name||Ibarayama Castle|
|Year Founded||Sengoku Period|
|Castle Condition||Ruins only|
|Historical Period||Pre Edo Period|
|Artifacts||Horikiri, Dorui, Dobashi, Kuruwa, &c.|
|Access||Kamishiro Station on the Ôito Line; 28 minute walk|
|Visitor Information||24/7 free; shrine|
|Time Required||30 minutes|
|Location||Hakuba, Nagano Prefecture|
|Coordinates||36° 39' 6.01" N, 137° 51' 47.77" E|
|Added to Jcastle||2022|
|Admin Year Visited||Viewer Contributed|
|Friends of JCastle|
|Shiro to Kosenjō|