Also known as: Misty Castle (霧ヶ城)

Iwamura Castle was built in 1221 by Tooyama Kagetomo, first daimyo of the Tooyama Clan and firstborn son of Katou Kagekado, senior vassal to Minamoto no Yoritomo of the Kamakura Shogunate. Located in south-eastern Mino Province (modern-day Iwamura Town, Ena District, Gifu Prefecture), it was considered one of Japan's three most famous mountaintop castles until it was ordered to be demolished during the Meiji Period.

Tooyama Kagetou, who became a retainer of Oda Nobunaga, was the last of the clan to hold the castle. Tooyama died of illness on Sept. 21, 1572 without an heir. Soon after, Takeda Shingen laid siege to the castle as part of his program of expansion. Tooyama's widow Lady Otsuya, aunt of Oda Nobunaga, negotiated for surrender of the castle.

Shingen entrusted it to Akiyama Nobutomo, one of his Twenty-four Generals. Lady Otsuya married Akiyama Nobutomo and sent her adopted son Gobomaru (Oda Katsunaga), fifth son of Oda Nobunaga, to Takeda as hostage.

In 1575, after Nobunaga defeated Takeda Katsuyori in the Battle of Nagashino, he laid siege to Iwamura Castle. Akiyama Nobutomo and Lady Otsuya defended the castle for six months, only emerging on Nobunaga's plea for peace and promise of safety. Nobunaga reneged on his word and had both of them executed as traitors by hanging upside-down.