Sashimi X-Wing Sudoku: How the Incomplete Fish Still Eliminates Candidates

Sashimi X-Wing Sudoku starts from a degenerate finned X-Wing

Sashimi X-Wing Sudoku follows one candidate across two base rows or two base columns, just like an X-Wing. In a normal X-Wing, the candidate is restricted to the same two cover columns in both base rows, creating four corners. A finned X-Wing adds one or more extra candidates near a corner. A Sashimi pattern goes one step further: after separating the fin area, the underlying X-Wing is incomplete because one of the expected fish corners is missing. The pattern can still work because the remaining candidates and the fin create a conditional trap inside one box. Do not identify Sashimi X-Wing Sudoku by shape alone. First confirm the base and cover structure for one digit, then identify which candidate or candidates are acting as fins, and finally check that the potential target lies in the limited intersection where both branches of the logic can reach it.

Use two cases to prove a Sashimi X-Wing Sudoku elimination

The safest way to verify Sashimi X-Wing Sudoku is with two cases. If a fin candidate is true, it removes the same digit from every peer in its box. If all fins are false, the remaining base candidates are forced into the reduced fish structure, and the aligned cover unit removes the digit from the target. A valid target is one that loses the candidate in both cases. This is why Sashimi eliminations are much narrower than ordinary X-Wing eliminations. You cannot sweep the whole cover column simply because the drawing resembles an X. Focus on the box containing the fin and on the cover line that the surviving fish candidate controls. If there are several fins, the target must be constrained by all relevant fin possibilities, not just one convenient cell. When in doubt, state the two branches explicitly before erasing anything.

Learn Sashimi X-Wing Sudoku after X-Wings and fins

Sashimi X-Wing Sudoku is easier to spot once ordinary X-Wings and Finned X-Wings are familiar. Scan one digit at a time and look for two rows with candidate positions that almost match across two columns, with the mismatch concentrated inside one box. Then ask whether removing the fin candidates would leave the necessary strong structure. If not, it is not a Sashimi pattern. Some Sashimi X-Wings can also be described with chain language, which is useful when the fish terminology becomes visually confusing. Shapedoku players can practice the same logic with symbols on Extreme boards: pick one shape, map its remaining positions, and treat strong links exactly as you would for a digit. The technique is about candidate identity, not number value. After a successful elimination, rescan the affected box and line for a hidden single or locked candidate before chasing another advanced fish.

When comparing Sashimi X-Wing Sudoku with a Finned X-Wing, imagine switching all fins off. If four clean rectangle corners remain, you have a finned X-Wing. If one expected corner is absent and the remaining structure still supplies the conditional fish logic, the pattern is Sashimi. This mental test is faster than memorizing several diagrams. It also prevents a frequent mistake: calling any broken X-Wing with an extra nearby candidate Sashimi. The missing corner, fin placement, and cover relationship must work together to prove the same target false in every branch.

• Work with one candidate value at a time.
• Identify two base rows or columns and the cover lines that form the near-X-Wing.
• Locate the fin area and confirm that the underlying fish is incomplete rather than simply broken.
• Test the fin-true case and the all-fins-false case separately.
• Eliminate only candidates that are false in both cases.
• Prefer a chain proof if the fish picture does not make the target relationship obvious.