Koyajō was built in the middle 16th century by the Maruyama Clan. The Maruyama Clan, which rivalled the Hiki Clan for control of the area, had formerly been the vassals of the Nishina Clan, but they later swore fealty to the Takeda Clan along with the Nishina themselves. With the fall of the Takeda in 1582, chaos erupted in Shinano. The resurgent Ogasawara besieged the Maruyama in their castles and Koyajō fell in 1583. Its last lord was Maruyama Morinao; he escaped to Uesugi territory to the north, becoming the castellan at Inariyamajō in 1584, and tried to fight a guerilla campaign.
Koyajō is a Sengoku period earthworks fortification site with a long profile which straddles the ridge overlooking Ikusaka Village. Ruins cover two wooded peaks. The first peak is very small, but beneath it are lined many terraces which climb the ridge like a set of stairs. The peak beyond that is the main bailey. A large double trench complex lurks beneath the main bailey. To the rear of the main bailey is a terraced sub-bailey and another trench. The castle mount is like a hill on the plateau-side north, being higher facing south, and this northern face has multiple bands of terracing lining it in parts. One can reach Hikiôjō by climbing from Koyajō, though I had long ran out of time for that by the time I came here.
|English Name||Koya Castle|
|Year Founded||Mid' 16th Century|
|Castle Condition||Ruins only|
|Historical Period||Pre Edo Period|
|Artifacts||Horikiri, Kuruwa, &c|
|Access||Bus from Akashina Station on the Shinonoi Line|
|Visitor Information||24/7 free; mountain|
|Time Required||40 minutes|
|Location||Ikusaka, Nagano Prefecture|
|Coordinates||36° 25' 41.27" N, 137° 56' 22.13" E|
|Added to Jcastle||2022|
|Admin Year Visited||Viewer Contributed|
|Friends of JCastle|