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.
Built in 1538 by Niwa Ujiyoshi, the castle sided with Oda Nobunaga and Tokugawa Ieyasu when they formed an alliance. After Nobunaga's death, the Niwa clan allied with Tokugawa Ieyasu.
During the Battle of Komaki and Nagakute in 1543, the head of the Niwa clan, Niwa Ujitsugu, went to Komakiyama Castle, Ieyasu's main camp, while his younger brother, Niwa Ujishige, defended Iwasaki Castle. While the battle was in a stalemate, Ikeda Tsuneoki, a general of Hideyoshi, led an army through the town of Iwasaki Castle towards Okazaki Castle in Mikawa Province, Ieyasu's main castle. Ujishige, with over 300 soldiers, met him in a desperate last stand.
Currently, there is a replica keep, but the dry moat and earthworks 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 can find a walking path that leads down to the dry moat, a suikinkutsu (water harp cave) in the second bailey's outwork, and remnants of earthworks and wells.
From the opposite side, with a large stone monument inscribed with "Iwasaki Castle" in the background, the gate and keep rise majestically after a short climb up some stairs, creating a magnificent sight.
Passing through the gate, you'll find a square enclosure where you're vulnerable to attacks from all sides. Though small, it's a great castle packed with enjoyable elements. 😊
Historically, according to materials at the Iwasaki Castle Historical Museum, the castle is said to have played a pivotal role in the Tokugawa victory during the Battle of Komaki-Nagakute, fought between Hashiba Hideyoshi (later Toyotomi Hideyoshi) and the combined forces of Oda Nobuo and Tokugawa Ieyasu. The valiant efforts of the 16-year-old castle lord, Niwa Ujishige, in the "Battle of Iwasaki Castle" played a key role in the Tokugawa victory. (Politically, Nobuo was swayed by Hideyoshi, so it's difficult to say who won...)
You can learn about the history of Iwasaki Castle and its surroundings at the Iwasaki Castle Historical Museum and within Iwasaki Castle itself.
While other places would likely charge around 500 yen for admission to each, it's completely free! 😳
Furthermore, while castle stamps usually cost over 300 yen at other castles, Iwasaki Castle's stamp was only 200 yen.
What a considerate castle!
The moat is still in good condition 🦈～
Amazing 🐬～
Also, it's helpful that admission and parking are free 🦈
