* Image is for illustrative purposes only.Minakuchi Castle (Hekisui Castle)
水口城（碧水城）
Minakuchi Castle (Hekisui Castle) is a historic castle in kinki dating from the Built in 1634 (Kan'ei 11), whose lord was Tokugawa Iemitsu (shogunal travel palace) / Kato Akitomo (first domain lord).
Overview
About the Castle
Minakuchi Castle is an exceptional fortress constructed in Kan'ei 11 (1634) in Koka, where the Tokaido and Nakasendo roads diverge and converge, as a rest castle built for the occasion of the third shogun Tokugawa Iemitsu's ascent to Kyoto (official visit to Kyoto). The shogun's ascent to Kyoto was a grand ceremony demonstrating the bakufu's authority, and the various daimyo along the route were obligated to maintain facilities suitable for the shogun's lodging. Among these, Minakuchi Castle was uniquely a shogun-exclusive rest castle constructed under direct bakufu control, and its magnificent palace buildings and perfect defensive facilities embodied the shogun's prestige.
Koka Region and the Iga Passage
Koka (Koga), where Minakuchi Castle is located, is a region world-renowned as a ninja heartland alongside Iga. The Koga ninja (Koga-shu) were employed by various daimyo from the Muromachi through Sengoku periods as specialists in intelligence and military operations, and their techniques formed a comprehensive martial arts system encompassing swords, throwing stars, poisons, and disguise arts. When Tokugawa Ieyasu undertook the "Iga Passage" (Iga-goe) immediately after the Honnō-ji Incident, the Iga and Koga ninja are said to have protected Ieyasu's party at the risk of their lives, and from this connection the Tokugawa house employed the Koga-shu as the bakufu's in-house ninja corps (oniwaban / secret intelligence unit).
Minakuchi Domain and the Kato Clan
After Iemitsu's ascent to Kyoto, Minakuchi Castle ceased its role as a shogun's rest castle, and in Tenna 2 (1682), Kato Aketo entered as lord of the Minakuchi domain with 20,000 koku. Subsequently, the Kato clan (later the Torii clan) continued as lords of Minakuchi domain until the end of the Edo period. Although modest in scale, Minakuchi Castle retained the dignity of a shogun's rest castle, and its stone walls, moats, and layout represented the finest of the bakufu's direct architectural techniques. The Minakuchi Castle site retains well-preserved stone walls and moats, and the reconstructed corner turret (Minakuchi Castle Museum) conveys the history of the shogun's rest castle.
Koka Culture and the Tokaido
Minakuchi flourished as a castle town and the 50th post-station (Minakuchi-shuku) on the Tokaido's 53 stations, and was also a lively post-town road where Omi merchants, daimyo on sankin-kotai (alternate attendance), and pilgrims traveling to Ise shrine passed back and forth.
Connection to Swords
Minakuchi Castle's connection to swords is rooted in the multi-layered samurai culture of this castle. Built as a shogunal lodging castle for Shogun Tokugawa Iemitsu's journeys to Kyoto, Minakuchi Castle stands in direct connection with the Tokugawa shogunate's sword culture. Iemitsu was a shogun with a profound interest in swords; the blades he carried on his journey to Kyoto were selected as the finest swords in the realm and served as "the shogun's side swords" (oshinshiraemono). When the shogun lodged at Minakuchi Castle, a custom developed whereby local daimyo and hatamoto presented famous swords to the shogun as tribute gifts. Through this exchange, the sword collections of both the shogunate and provincial daimyo were enriched. Minakuchi is situated in Koga, known as the home of the ninja. Swords and short swords were essential components of the Koga ninja's weaponry. The "ninja-to" (ninja sword) used by the Koga ninja were shorter and straighter than ordinary swords, with practical designs specialized for close-range combat in darkness and rapid escape. Koga swordsmiths, responding to ninja demand, produced practical short swords and wakizashi, and their techniques formed one aspect of Omi Province's sword culture. Omi Province possessed its own unique smithing collective known as "Goshu-mono" (Omi-made), and smith-masters active around Nagahama and Hikone in Omi continued their blade-forging under the protection of the Ii clan. The Kato clan, which received the domain of Minakuchi Castle, was descended from Kato Yoshiaki, one of the Seven Spears of Shizugatake (with Kato Akitomo, Yoshiaki's grandson, as the first daimyo), and inherited a sword-collecting tradition rooted in Yoshiaki's renowned martial prowess. The Minakuchi Castle Museum presents exhibitions on the history of the shogun's lodging castle and Koga samurai culture; combined with the nearby Koga Ninja Mansion (Koga-ryu Ninjutsu Mansion), visitors can experience two contrasting dimensions of weapon culture—the blades of the samurai and the tools of the ninja.
Highlights
- Minakuchi Castle ruins (stone walls and moat) — precision Edo-period shogunal construction
- Minakuchi Castle Museum (reconstructed corner turret) — shogunal travel palace history and Koka warrior culture
- Koga Ninja Mansion — authentic ninja house maintained by ninja descendants (National Historic Site)
- Koka Ninja Village — shuriken throwing, ninja museum, and Koga-shu history
- Minakuchi-juku Tokaido post station townscape
- Taro family Jin'ya ruins — the Tokugawa deputy's residence in Koka
* Opening hours and admission fees are subject to change. Please check the official website before visiting.