Japanese Castle Parts: Tenshu, Ishigaki, Honmaru and the 12 Original Keeps

The core idea: rings of defence from the moat to the keep

Every part of a castle answers one question: how do you slow an attacker down? With layers. A moat, hori (堀), keeps attackers at a distance. Behind it rises a stone wall, ishigaki (石垣), literally stone fence. A gap in the wall is a gate, mon (門), and behind the gate lies a flat, walled enclosure, a maru (丸). Then the pattern repeats, closer to the centre, until you reach the keep.

The plan below shows the ideal version with three rings. Follow the dashed path from the main gate: it turns at every layer, so an attacker who breaks one gate still faces a long walk under fire to the next. Real castles bend it around rivers and hills. Tickets, shoes and photo rules belong to the separate guide to visiting gardens and castles; this one is about the buildings. Friends at the entrance might say the lines after the plan.

UnihongoTravel Japanese

大手おおて門もんから入りはいりましょう。Let's go in through the main gate.

The rings and the gates

The rings are numbered from the inside out: the centre came first. Some castles add rings named for a direction, such as the nishinomaru, the western circle, at Himeji.

Gate names come from warfare. Ōte, literally big hand, meant the main force attacking from the front, so the ōtemon is the front gate; Kōchi Castle writes it 追手門, the pursuing side, with the same reading. Karamete, from karameru, to seize, was the force that struck from behind, so the karamete-mon is the back gate. A guide leading a group inward might say:

The keep, part by part

The keep repeats the rings upwards. It stands on a stone platform, the tenshudai (天守台). Its lower walls are pierced with small openings for bows and guns, sama (狭間). At the corners, bays jut out over the stone wall with hatches in their floors: ishi-otoshi (石落とし), literally stone droppers. The name says stones, but Matsumoto Castle's own guide describes its eleven ishi-otoshi as openings for firing guns downwards. The top floor, saijōkai (最上階), is the lookout.

Gables, hafu (破風), come in triangular chidori-hafu and curved kara-hafu, often mainly for looks. At both ends of the top ridge sit the shachihoko, charms against fire. After the drawing come things you might say to a friend while pointing out these parts.

UnihongoTravel Japanese

あの出っ張りでっぱりは石いし落としおとしです。That part sticking out is an ishi-otoshi.

Confusable pairs: jū and kai, tenshu and tenshukaku

Boards describe a keep with two numbers, such as gojū rokkai (五重六階). Jū (重), literally layer, counts the roofs you see from outside; kai (階) counts the floors inside. They often differ, because a floor can hide under a roof. Matsumoto Castle's official site calls its keep the oldest surviving one of five tiers and six floors. Some books write sō (層) for the outside count.

A volunteer guide explains.

Beyond the basics: reading a stone wall

Stone walls changed a great deal around 1600, and boards often name the technique. Matsumoto Castle's guide notes that its keep's base is nozura-zumi with sangi-zumi corners, never re-laid in 400 years. Walls that curve to near-vertical at the top are called musha-gaeshi, literally warrior repeller; Kumamoto Castle is the famous example. On a guided walk you will hear sentences like these.

The twelve original keeps: genzon tenshu

Of the many keeps once built, twelve survive from the Edo period or earlier: the genzon tenshu (現存天守), literally existing keeps. Twenty were still standing into the 1940s; air raids in 1945 and a fire in 1949 destroyed eight of them. All twelve are Important Cultural Properties, and five are National Treasures. Visiting all twelve is a popular goal.

Shikoku, the smallest main island, has four of the twelve; Kyūshū and Hokkaidō have none. After a name, 城 is read jō.

Original or rebuilt: what the board at the entrance says

Most keeps you will visit were rebuilt in the twentieth century, many in concrete after the war, and the entrance board says which kind you are seeing. The terms form a scale of faithfulness, though experts draw the lines differently.

• Genzon tenshu (現存天守): original, standing since the Edo period or earlier.
• Mokuzō fukugen (木造復元): rebuilt in wood from plans, photographs and excavation, using traditional methods; Kakegawa (1994) and Ōzu (2004) are examples.
• Gaikan fukugen (外観復元): the exterior copied from records, usually in concrete, often with a museum inside.
• Fukkō tenshu (復興天守): rebuilt where a keep once stood, with a partly guessed design; Osaka Castle's keep of 1931 is the oldest surviving example.
• Mogi tenshu (模擬天守): a keep-style building at a castle that never had a keep, or whose keep is undocumented.

Ato (跡), literally trace, marks what is gone: a sign reading 本丸跡 or 天守台跡 means the site, not a building.

Reading the boards and signs

Explanation boards, setsumeiban, use a formal written style with passive verbs: saiken sareta, was rebuilt; shitei sarete iru, is designated. Reading one with a friend, you will meet sentences like the first six below; the last two are warning signs along the walls.

Common mistakes when talking about castles

Saying Himeji-shiro. Learners meet shiro, castle, first and attach it to names. After a place name it becomes jō: Himeji-jō. Alone, or as o-shiro, it stays shiro.

Assuming every old-looking keep is original. From outside, a concrete rebuild can look just like a genzon tenshu. Check the board first.

Counting floors from the roofs. The cause is treating jū and kai as the same number. Count roofs from outside and floors inside, and expect them to differ.

Calling every tower a tenshu. Yagura can be three storeys high and look like small keeps. The tenshu is the main tower, sometimes with smaller attached keeps; the rest are yagura.

Picturing maru as round. Maru literally means circle, so learners expect round walls. Here it means an enclosure, and most are angular.