After that, the Isshiki clan held Takebeyama-jo Castle for several generations until 1579 when Yusai HOSOKAWA attacked Tango under the orders of Nobunaga ODA, and the Isshiki army barricaded themselves in the castle after losing each battle fought, but eventually fell under the Hosokawa army's fierce attack.
その後は代々一色氏の居城としてつづいたが、1579年（天正7）に織田信長の命を受けた細川幽斎が丹後を攻撃、各地で敗れた一色軍は建部山城に篭城するが細川軍の猛攻の前に崩壊する。