Matsuo Anaguma.

How it goes together

The king is in the corner on 9i, behind the lance on 9h, with the left silver on 8h as the lid. Where the ordinary Static Rook Anaguma keeps a gold on 7i, this one has a silver: the right silver, walked back from 5g through 6h. The golds stand on 7h, beside the lid, and on 6g, one step up and to the right, behind the 6f pawn. The two silvers guard each other, and the 7h gold guards both of them and the 6g gold. The bishop stays on 7g.

Move by move

Black only, from the start position. The first ten moves are the Static Rook Anaguma’s own; then the 6f pawn closes the bishop’s diagonal, the king goes in, and the generals arrive one at a time, the right silver last.

Seventeen moves, two more than the Static Rook Anaguma. The silver on 7i is the castle’s mark: in the ordinary Anaguma that square holds a gold. A review of Watanabe Akira’s book on beating the Fourth File Rook calls the arrival of that silver a very good result for the static rook, which is why the ranging rook’s usual tries come before it.

What it is good against

Four generals, all touching. The silvers on 8h and 7i guard each other, and the 7h gold guards both. Shogi Wars says it holds up better than the gold-on-7i Anaguma against attacks from above, such as an edge attack: if the 8h silver is pulled away to the edge, the 7i silver steps up to 8h and closes the lid again. The bishop can drop back to 6h and work from there. A saying quoted from Watanabe Akira’s book: if you get it built, you win eight games in ten.

Where it breaks

Time. It costs seventeen moves, and the last two, the silver walking back, are when the opponent strikes: against the Fourth File Rook the usual tries are a pawn to 5e or a silver to 5c before the castle is closed. With four generals at home, the attack is left to the rook, the bishop and the knights. A promoted pawn that reaches the castle can peel off the silvers next to the king.

When to build it

Static rook against ranging rook, when the opponent lets you take your time. ja.wikipedia describes it as the shape a static rook threatens to switch into against the Fourth File Rook, and the one it aims for against the Cheerful Central Rook; shogi-gym adds that it is easiest to build against the Third File Rook. It is named after Matsuo Ayumu, who played it often, although he has said the shape existed before him.