Visited on February 22, 2026.
This is an earthen castle, but the ruins show a completely unfounded imitation castle tower built in the main enclosure in a Showa-era sensibility. The value of this castle ruin lies in its earthworks, dry moats, and the story of the Battle of Komaki-Nagakute. The dry moat is magnificent. During the Battle of Komaki-Nagakute, Niwa Ujishige, who was staying at the castle while he was away, provoked Ikeda Tsuneoki's army of 7,000 (with 3,000 reinforcements) heading for Okazaki Castle, despite only having 200-300 defenders, and was attacked and annihilated. This marked a turning point in Ieyasu's army catching up with Ikeda's army. As expected, just over 200 men were not enough to defend the castle.
It was built by Niwa Ujikiyo in 1538 (Tenbun 7). When Oda Nobunaga and Tokugawa Ieyasu formed an alliance, the Niwa clan allied with Oda Nobunaga, and after Nobunaga's death, they allied with Tokugawa Ieyasu.
During the Battle of Komaki and Nagakute in 1543 (Tensho 12), Niwa Ujitsugu, the head of the clan, headed for Komakiyama Castle, Ieyasu's main camp, while his younger brother Niwa Ujishige defended Iwasaki Castle. As the battle reached a stalemate, Hideyoshi's subordinate Ikeda Tsuneoki led an army through Iwasaki Castle and advanced toward Ieyasu's main castle, Okazaki Castle in Mikawa Province, but Ujishige met them with over 300 castle soldiers and was killed in battle.
Currently, there is a mock castle tower, and the dry moat and earthen ramparts remain.
During the Battle of Komaki and Nagakute, the castle lord, the Niwa clan, who sided with Ieyasu, attempted to block the Hashiba forces marching towards Okazaki from that direction. With only 300 men, they fought against 7,000 and the castle fell.
However, this delay allowed Ieyasu's main force to catch up, influencing the subsequent battles.
The castle tower is a replica, but it enhances the castle's atmosphere and is quite impressive.
While many genuine remains still exist, the castle itself wasn't particularly large, so you can see everything relatively quickly.
There is free parking, and admission to the replica castle tower's observation tower and the historical museum is also free.
Approaching Iwasaki Castle from the parking lot, you'll find a promenade that leads down to the dry moat, a suikinkutsu water fountain in the Ninomaru horse-shed, and remnants of earthworks and wells.
From the other side, a large stone monument bearing "Iwasaki Castle" appears in the background, and a short staircase leads to the impressive gate and castle tower.
Once through the gate, you'll find a masugata (square-shaped enclosure) that offers ample opportunity for attack from all sides. It's a small castle, but packed with fun elements. 😊
Historically, according to documents from the Iwasaki Castle Historical Museum, the valiant efforts of 16-year-old castle lord Niwa Ujishige in the Battle of Komaki and Nagakute, between Hashiba Hideyoshi (later Toyotomi Hideyoshi) and the allied forces of Oda Nobukatsu and Tokugawa Ieyasu, are said to have paved the way for the Tokugawa's victory. (Politically, Nobukatsu was manipulated by Hideyoshi, so it's hard to say who won...)
You can learn about the history of Iwasaki Castle and the surrounding area at the Iwasaki Castle Historical Memorial Museum and inside the castle.
While other places would likely charge around 500 yen for admission, it's free! 😳
What's more, while the castle seal at other castles would cost over 300 yen, it was only 200 yen at Iwasaki Castle.
What a very reasonable castle!
The moat is still in good condition 🦈～
Amazing 🐬～
Also, it's helpful that admission and parking are free 🦈
