* Image is for illustrative purposes only.Oka Castle
岡城
Oka Castle is a historic castle in Kyūshū dating from the Founded ca. 1185 (Bunji 1), whose lord was Nakagawa Hidenari.
Overview
About the Castle
Oka Castle is a mountain castle located in Taketa, Oita Prefecture, standing on a highland plateau at an elevation of 325 meters where the Ōno River and Inaba River—flowing down the slopes of Mount Aso—carve deep gorges. According to tradition, the fortress was constructed in the first year of Bunji (1185) by Ogata Saburō Koremasa to obstruct the pursuers of Minamoto no Yoshitsune. Subsequently ruled by the Ōtomo and Shiga clans, in the third year of Bunroku (1594), Nakagawa Hidenarī entered the castle and it was developed as a modern-era castle structure. The dry-stone walls, rising over 20 meters high and stacked in layers along the mountain ridge, are highly regarded as Oita's finest castle landscape.
Taki Rentarō and "The Moon Over the Ruined Castle"
The primary reason Oka Castle is known throughout Japan is the composition "Kōjō no Tsuki" (The Moon Over the Ruined Castle), which composer Taki Rentarō drew inspiration from while contemplating this castle's ruins. Rentarō spent his boyhood in Taketa, where his father was stationed, and the ruins of Oka Castle became his playground. In Meiji 34 (1901), he set to music a poem by lyricist Doi Bansui, creating "The Moon Over the Ruined Castle," which remains one of the finest masterworks of modern Japanese art song, still widely sung today. The lyrics, beginning with "Spring in the high tower, a feast of blossoms...", express the transience of glory and decline through the light of the moon, perfectly mirroring the desolate beauty of Oka Castle's ruins. Today, a bronze statue of Taki Rentarō stands at the castle ruins, and stone monuments inscribed with "The Moon Over the Ruined Castle" are positioned throughout the site—a castle where the melody of the famous song drifts through the spring cherry blossoms, autumn foliage, and winter snow.
The Nakagawa Family and the Culture of Oka Domain
Nakagawa Hidenarī, who entered Oka in the third year of Bunroku (1594), was transferred from Miki Castle in Harima and made extensive modern renovations to Oka Castle. The Nakagawa family was a lineage of military commanders who served under Toyotomi Hideyoshi during the Toyotomi administration, and during the rule of the 70,000-koku Oka domain, they devoted themselves to the promotion of scholarship and martial arts. The domain school "Yugakukan" maintained a high standard even among the clan schools of Kyushu, and in the late Edo period produced many patriots dedicated to the restoration movement and imperial loyalism. Among figures from Oka domain, Miura Baien, a Meiji-era philosopher, stands out as an exceptional scholar.
Stone Walls and the "Castle in the Sky"
Oka Castle's stone walls, employing a rough-stone-stacking method as their foundation, demonstrate high technical sophistication, with layers of tall stone walls stacked along the mountain ridgeline, creating particularly mystical beauty when mist descends or winter snow blankets the site. Sometimes called the "Castle in the Sky" or the "Castle of Mist," photographers gather at dawn hoping to capture the fortress walls floating amid the cloud sea. In spring, the contrast between cherry blossoms and stone walls is exquisite, and many tourists visit during the Oka Castle Cherry Blossom Festival.
Oita's Hot Spring Culture and Oka Castle
Taketa City lies within one of Oita Prefecture's hot spring regions, with nearby attractions including Nagayu Hot Spring (one of Japan's finest carbonated springs) and Kuju Highland, making hot spring travel combined with Oka Castle sightseeing popular. The castle town of Taketa retains a retro streetscape, and by visiting both the "Taki Rentarō Memorial Hall" and the Taketa City History and Culture Hall "Yugakukan," one can deeply appreciate the historical and cultural legacy of Oka Castle and Oka domain.
Connection to Swords
Oka Castle's connection to swords can be discussed from three perspectives: Kyushu's southern sword culture and the Nakagawa clan's promotion of martial arts, and the samurai aesthetics symbolized by "Kōjō no Tsuki." The warriors of Oka domain were shaped by Kyushu's sword culture, and particularly in Bungo Province (Oita Prefecture), which was controlled by the domain, distinctive sword schools flourished. During the Otomo clan's rule of Bungo, firearm culture from southern barbarian sources spread rapidly, and a unique weapon culture coexisting swords and firearms took root in the region. Nakagawa Hideoshige was a battle-hardened general who served under Toyotomi Hideyoshi (then known as Hashiba Hideyoshi) and participated in campaigns throughout the land; he is believed to have possessed swords bestowed by Hideyoshi and celebrated blades acquired in battle. Some swords and armor inherited through the Nakagawa clan are preserved in the Taketa City Historical Materials Museum, conveying the pride and aesthetic sensibility of the Nakagawa family as warriors. Bungo, where Oka Castle stands, is also renowned as a center of "Bungo smithy" production. Among Bungo blades, the Takada school is known for creating many practical swords spanning the Nanbokuchō through Muromachi periods. Even further back, Kunihira of Bungo (Kichinoshindayu Kunihira), active from the late Heian into the early Kamakura period, was celebrated as a master craftsman selected as imperial sword smith for Emperor Gotoba. The character of Bungo swords is their robust construction and keen edges—they represent the typical blades favored by Kyushu warriors in actual combat. What "Kōjō no Tsuki" symbolizes is the spirit of warrior beauty amid the transience of rise and fall; it resonates deeply with the Japanese sensibility that the Japanese sword transcends mere weapon to embody "mono no aware," the artistic expression of impermanence itself. The moonlight descending upon the stone walls of the ruined castle and the keen hamon of a blade forged with the smith's soul—these two flow from the same wellspring of Japanese aesthetics. Sword enthusiasts who visit Oka Castle can most directly sense the spiritual ground of samurai culture from which the Japanese sword was born by humming "Kōjō no Tsuki" as they walk the stone walls.
Highlights
- Magnificent dry-stone walls — walls over 20 meters high trace the mountain ridgeline in Oita's finest castle landscape
- Taki Rentarō statue and 'Kōjō no Tsuki' monuments — the birthplace of a beloved song, spectacular with cherry blossoms or snow
- Sea of clouds castle — on misty mornings, the walls emerge from fog in an ethereal spectacle
- Taketa City Historical Museum 'Yugakukan' — displays Nakagawa clan armor, swords, and domain records
- Taki Rentarō Memorial Museum — chronicles the composer's life and the creation of 'Kōjō no Tsuki'
- Nagayu Onsen — one of Japan's premier carbonated hot springs, about 30 min by car from Oka Castle
* Opening hours and admission fees are subject to change. Please check the official website before visiting.