Duck.

How it goes together

The king steps up one square to 5h. The two silvers stand on either side of him, on 6h and 4h, and the golds go outward along the bottom rank to 7i and 3i, next to the knights. The pawns from 7g to 3g never move. Those are the duck’s two feet: a silver and a gold on each side, each guarding the other. Every empty square on the bottom two ranks is covered by at least one piece, which is what the sources mean when they say there is no gap for a drop. Its other name is 御神酒指し.

Move by move

Black only, from the start position, in the order shogi-rule.com animates it: the rook pawn and the floating rook, the bishop out to the edge, then the castle.

Ten moves. The bishop on 9g looks out from the edge instead of opening its diagonal, and the rook on 2f, floating in front of the camp, answers the opponent’s rook-pawn exchange, so neither needs a gold beside it, and the golds are free to go wide.

What it is good against

Drops. With nowhere in its own camp for a rook or bishop to land, the Duck player can hand over major pieces in trades that would be reckless with any other castle, and often forces those trades even at a cost in material. It can be built against a static rook or a ranging rook.

Where it breaks

Making an attack. All four generals defend, so the attack is left to the rook, the bishop and the edge lance. Katō Jirō called the shape beautiful but unable to develop, like a doll. Against a patient opponent who keeps his silvers behind his pawns, a Yagura above all, it is hard to start anything, and once broken it falls quickly. The bishop’s head on 9f is guarded only by the rook.

When to build it

As a surprise by a static rook, mostly against another static rook (shogi-rule.com, shogi-gym, en.wikipedia), with lines against a ranging rook too. ja.wikipedia says it is not seen in professional games but is fairly popular with amateurs.