Yamagata Castle was the seat of Mogami Yoshiaki, a leading warlord of the Tohoku region and uncle of Date Masamune. After siding with the Eastern Army at Sekigahara, the Mogami rose to rule 570,000 koku. The ruins are preserved as Kajo Park, with reconstructed gates and surviving stone walls, and serve as a celebrated spot for cherry blossoms.

Yamagata Castle is traditionally said to have been founded in 1357, when Shiba Kaneyori entered Dewa Province and established his residence. His clan later adopted the name Mogami and ruled the region for roughly 250 years. During the Sengoku period, Mogami Yoshiaki (1546–1614) consolidated the clan…