What is Samurai Sudoku?
Samurai Sudoku (also called Gattai-5, "five joined" in Japanese) is the most spectacular variant of classic Sudoku. It consists of five 9×9 grids arranged in a cross, sharing four 3×3 blocks at the corners. The result is a 21×21 surface with a total of 369 active cells to solve simultaneously.
Each of the five grids (four corner + one central) is a complete, valid 9×9 Sudoku in its own right. Solving them means deducing numbers that serve several grids at once thanks to the shared boxes.
Origin and popularity
Samurai Sudoku was created by Bryce Williams in the United States in the early 2000s and popularised by the magazine Sudoku Master. Today it appears in premium puzzle books, weekend newspapers and international competitions such as the World Sudoku Championship.
Samurai Sudoku rules
- The standard Sudoku rules apply to each of the 5 nine-by-nine grids.
- The 4 shared boxes (where the corner grids overlap the central one) must satisfy the constraints of BOTH grids at once.
- The cells outside the 5 grids are inactive zones and are shown blank.
Strategy for the Samurai
The key lies in the shared boxes: when you deduce a number in a shared cell, that value affects two sudokus simultaneously. It’s usually most rewarding to start with the central grid, since it shares boxes with all four corners and every move unlocks clues in four directions at once.
How long does it take?
An average player takes between 40 and 90 minutes to complete a normal-difficulty Samurai Sudoku. Experts solve it in around 25-35 minutes. It’s the perfect challenge for a quiet afternoon or a long trip.