Tsurumaru Castle, also known as Tsurumaru-jo, is a historic Japanese castle located in Kagawa Prefecture. Originally built in the late 16th century by Miyoshi Nagayoshi, it served as a strategic military stronghold during the Sengoku period. The castle features a unique design with a central keep and surrounding moats, reflecting traditional Japanese castle architecture. Today, the site is a popular tourist destination, offering visitors a glimpse into Japan's feudal past. Although much of the original structure has been lost over time, the remaining ruins and reconstructed elements provide insight into the castle's historical significance and its role in regional defense.