Silver Mino.

How it goes together

Start from a Half Mino: king 2h, silver 3h, gold 4i. Push the 6f pawn, walk the left silver up from 7i to 7h and 6g, and then step it diagonally back to 5h, the square where a Mino puts its left gold. The 4i gold guards both silvers, and both silvers guard the gold diagonally from above. Both silvers also guard the 4g pawn. The left gold stays at home on 6i.

A Silver Mino starts as a Half Mino: the first six moves below are that castle, and four more bring the left silver round.

Move by move

Black only, from the start position. The first six moves are the Half Mino. No source gives the order of the last four: they are the left silver’s only road to 5h with the rook on 6h and the 5g pawn at home, and the first three of them are the ordinary ranging rook development of that silver.

Ten moves, three more than a Mino. The silver ends on the gold’s usual square, and the left gold never moves from 6i.

What it is good against

How the pieces hold together. The 4i gold guards both silvers and both silvers guard the gold, and ja.wikipedia and Shogi Wars both say the generals connect better than in a plain Mino. The left gold is not part of the castle, so it is free for other work: shogi-joutatsu says the shape turns up when that gold is defending on the eighth-file side.

Where it breaks

The squares beside the silvers. A silver has no sideways move, so 4h, between the two silvers, is guarded by the 4i gold alone, where a Mino guards it with both golds. Shogi Wars names that square as the weak point, and ja.wikipedia the left silver’s flank (横腹). It also costs three more moves than a Mino, and ja.wikipedia says it has many faults.

When to build it

A ranging rook castle, seen now and then in place of the Mino when the left gold has work elsewhere. No source names an opening that aims for it from the start.