Introduction The earliest known castle built in Japan is Inuyama Castle, which dates back to 1440, located in present-day Inuyama, Aichi Prefecture. The need for castles in Japan increased during the 15th century when the country’s central government began to weaken and Japan entered the “Warring States”, also known as the Sengoku Period, which lasted from 1467 to 1615. Up to 5,000 castles were built from this era onwards, …