Sashimi Swordfish Sudoku: The Finned Fish That Still Works

A Quick Refresher on the Swordfish

Before the sashimi form, meet the plain swordfish. Pick one digit and find three rows where it can go in only two or three columns, and where all those placements fall within the same three columns overall. Then that digit must fill those three columns using the three rows, so it cannot appear elsewhere in the columns. You eliminate the candidate from every other cell in those three columns. That is a standard fish, the parent of sashimi swordfish sudoku.

Swap rows and columns and the same logic runs the other way. Fish are symmetric like that, which is part of their charm.

Fins and the Sashimi Twist

Real puzzles rarely give you a perfect fish. Often there is one extra candidate, called a fin, that spoils the clean pattern. A finned fish still works, but only for cells that can see the fin. Sashimi swordfish sudoku goes a step further: it is a finned swordfish where, if you removed the fin, one of the three base sets would fall apart because a corner is missing. The pattern is technically incomplete, yet the fin holds it together.

The name paints the picture. A sashimi fish is a fish with a piece cut away, kept alive only by its fin. Despite looking broken, the elimination logic is perfectly valid.

How to Read the Eliminations

The rule is the same as any finned fish. The candidate can be removed only from cells that both belong to a cover column and can see every fin. In sashimi swordfish sudoku, the missing corner means fewer base placements, so you must be careful, but the payoff cell is still forced.

1. Choose a digit and look for a near-swordfish across three lines.
2. Spot the fin, the stray candidate that breaks the clean shape.
3. Notice that without the fin one base line would collapse, marking it sashimi.
4. Eliminate the digit only where a cover cell also sees all fins.

Why Bother With Sashimi Swordfish Sudoku

Beginners sometimes skip finned and sashimi fish because they look messy, but that is a mistake. Sashimi swordfish sudoku shows up often precisely because clean fish are rare, so learning the finned logic roughly doubles how many fish you can actually use. It is one of the best returns on effort in advanced solving.

The eliminations are just as reliable as a textbook swordfish, since the fin only narrows which cells you may target, never weakening the underlying proof.

Training on Shapedoku

Fish are single-digit patterns, which makes them ideal for Shapedoku, where you can lock onto one glowing shape and scan its candidates across the grid. To hunt sashimi swordfish sudoku, keep pencil Notes on, pick a shape, and look for three lines that almost form a fish with one stray candidate as the fin. The dark, uncluttered board keeps the pattern visible.

These appear on Hard and Extreme puzzles, so treat them as a step up from basic X-Wings. Once the fin logic clicks, sashimi swordfish sudoku becomes a dependable tool rather than a scary curiosity.