What are the rules of tsume shogi?

The attacker must give check with every move. The defender holds every piece not on the board or in the attacker’s hand and plays the longest defence. The problem must have exactly one solution, and the attacker’s hand must be empty at mate.

What is mudaai in tsume?

Mudaai (無駄合) is a futile interposition: a block that only lets the attacker capture the piece and mate as before. It is not counted as a reply.

Yozume (余詰) is a second solution to a tsume problem, most often a different first move that also mates within the stated length. It is a flaw that makes the problem unsound.

Does the defender get all the remaining pieces in tsume?

Yes. By convention every piece that is not on the board and not in the attacker’s hand belongs to the defender and can be dropped to block a check.

Tsume Rules: How a Shogi Mate Problem Is Solved (Mudaai, Yozume and the Rest)

Two sides with different rules

The attacker (攻方, semekata) is you, playing up the board. Every move must be check. A quiet move that would mate faster is not a solution.
The defender (玉方, gyokukata) has only the king and whatever stands on the board, plus every piece that is not on the board and not in your hand. They may drop any of those to block a check.
The defender always plays the reply that takes longest to mate. The stated length, “mate in 3”, is counted in plies against that best defence: your move, theirs, yours.
The mate must be real: the ordinary rules still apply, so the final move may not be a dropped pawn (uchifuzume) and no piece may end on a square it can never leave.

A worked example

A three-ply problem from the app’s library. Black to play. Black’s hand is below the board; above it is the defender’s, which is every other piece in the set.

Solution: ▲G*2c △K-2a ▲G-2b. Each black move is a check, and white’s reply is the one that lasts longest.

Blocking a check

Because the defender holds so many pieces, blocking a long-range check is the defender’s main resource, and the genre names its forms:

合駒 (aigoma): any piece put between the king and the checker.
中合 (chūai): a block placed at a distance from the king, not next to it. Capturing it can put the attacker’s piece on a worse square, turn a later drop into uchifuzume, or leave the attacker holding the wrong piece. Often the hardest defence in a problem.
移動合 (idōai): a block made by moving a piece already on the board rather than dropping one.
限定合 (gentei-ai): a block where only one piece type gives the longest resistance, so the defender’s choice of piece is forced and the main line is fixed.

Futile interpositions do not count (無駄合 mudaai)

If a block only lets the attacker capture the blocking piece and mate exactly as before, it is 無駄合, a futile interposition, and it is not counted as a reply. Without this rule the defender could stretch any mate by dropping pieces into the gap, and “mate in 3” would mean nothing. The All Japan Tsume Shogi Federation (全日本詰将棋連盟) states it this way, and it is why the app accepts the short solution even when a pointless block is technically legal.

What makes a problem unsound

A composed problem must have exactly one solution, found in the stated number of moves. The named flaws:

余詰 (yozume): a second solution, usually a different first move that also mates in time. A problem with 余詰 is broken, with one conventional exception: a choice on the very last move (最終手余詰) is tolerated.
駒余り (koma-amari): the attacker still holds a piece at mate. In a sound problem the hand is empty at the end.
早詰 (hayazume): a mate shorter than the stated length exists.
不詰 (futsumi): the defender has a way out, so there is no mate at all.

How the app’s problems are checked

All 1,561 problems in Shogi Castle pass our own checks: the starting position breaks no rule of the game (no two unpromoted pawns of one side on a file, no piece that could never move again, no second king, no more pieces than one set holds, and the side that just moved not left in check), the solution replays, every attacking move is a check, it ends in mate at the stated length, the hand is empty at mate, futile drops are not counted as replies, and a search at every ply, within its node budget, found no independent second solution.

The few alternatives the genre tolerates, such as promoting or not, or the same piece dropped further back, are accepted as correct. Problems that failed any of these were dropped, not patched. The position check was added on 3 October 2026, after a reader found a problem with two of one side’s pawns on one file; 166 problems failed it and were removed.

How a mate problem is played.