The castle was originally built on a small island called Nyūjima, which was later connected to the mainland via land reclamation.
The castle was the stronghold of the Ōtomo clan, a powerful Sengoku-era dynasty that converted to Christianity and established trade with Portugal.
Because of the castle's connection to the Ōtomo clan, the local area remains a center for 'Kirishitan' (Christian) history in Japan.
The site retains original stone walls constructed with 'nozurazumi' technique, where stones are piled without being shaped.
A portion of the site is designated as a historic landmark of Oita Prefecture.
Usuki Castle Ruins, also known as Nyūjima Castle, was originally constructed by Ōtomo Sōrin in 1562. The site is uniquely situated on a former island, now connected to the mainland, which gave it a strategic maritime advantage. The stone walls, originally built to be surrounded by the sea on three sides, remain the primary historical feature. While the main structures were dismantled during the Meiji Restoration, the site preserves original gate remnants and a reconstructed turret. The castle grounds now function as a public park, particularly known for over 800 cherry trees blooming in spring. Visitors can explore the preserved stone ramparts and the foundation layouts of the former lord's residence. The area provides a clear view of the surrounding Usuki port and old town district.
The view from the top of the reconstructed turret platform overlooking the castle grounds and the bay.
Wear comfortable walking shoes, as the site involves climbing stone steps and gravel paths.
Combine your visit with a walk through the nearby Nio-za Historical Road to see traditional merchant houses.
Visit during the cherry blossom season to see the park illuminated in the evening.
Do not mistake the modern town surrounding the hill for the original castle layout, which is concentrated on the hilltop park.
Respect the site as a historical park by not climbing on the stone walls or damaged ruins.
