The castle was likely built by Yamada Naosada, a retainer of Ueda Tomonao as one of the outlying fortifications to Matsuyama Castle, about 14km away. In fact there are several castles along this line. From Koshigoe Castle, you'll find Aoyama Castle, Ogura Castle, Sugaya Yakata, and Aoto Castle in one defensive line stretching back to Matsuyama Castle. About 2km to the northwest of Koshigoe Castle is a another small castle called Yasuto Castle. It was likely a sub fortification of Koshigoe Castle or a location for sending smoke signals. The detailed history of Koshigoe Castle after this and it's eventual demise is not well documented but it was likely abandoned after Matsuyama Castle fell in Hideyoshi's campaign against the Hojo in 1590.
There's also a bus that runs roughly every hour from the Ogawamachi Station to the Patoria Ogawa Health Center. From here it is a short walk through the parking lots and across the street to find the trail to the top of the mountain. There are plenty of signs and the diorama shown in one of the pictures below is also from the parking lot near the health center.
|English Name||Koshigoe Castle|
|Year Founded||late 15th C to early 16th C.|
|Castle Condition||Ruins only|
|Designations||Prefectural Historic Site|
|Historical Period||Pre Edo Period|
|Access||Ogawamachi Sta. (Tobu Tojo Line) walk 60 mins.|
|Visitor Information||trails open any time|
|Time Required||75 mins|
|Location||Ogawamachi, Saitama Prefecture|
|Coordinates||36° 2' 40.06" N, 139° 13' 56.42" E|
|Added to Jcastle||2015|
|Admin Year Visited||2015|
|Admin Visits||February 14, 2015|