The History of Hitori: Nikoli's Number-Elimination Puzzle

Hitori has the feel of a puzzle that has been around forever, a quiet grid of numbers you shade away one by one. In fact it is a modern invention with a clear birthday, a famous publisher, and an unusual mechanic that set it apart from almost every other number puzzle of its era. It comes from the same Japanese workshop that gave the world Sudoku, and its story is a neat example of how a clever idea can travel from a Tokyo puzzle magazine to screens and newspapers around the globe. Here is where Hitori came from. When you are done, you can play one yourself.

A puzzle from the house of Nikoli

Hitori was created and popularised by Nikoli, the legendary Japanese puzzle publisher. That name carries weight: Nikoli is the company that took an obscure American puzzle, refined it, renamed it Sudoku, and sparked a worldwide craze. The same workshop is behind a whole family of beloved logic puzzles, including Kakuro, Nurikabe and Slitherlink, and Hitori is one of its most distinctive.

Hitori first appeared in Nikoli's flagship magazine, Puzzle Communication Nikoli, in issue #29, published in March 1990. Like all Nikoli puzzles, it was built on a strict design philosophy: every puzzle is handcrafted rather than churned out by a computer, has exactly one solution, and can be solved by logic alone, with no guessing. That commitment to elegant, fair puzzles is a big part of why Nikoli's titles feel so satisfying, and Hitori is a fine showcase for it.

An unusual idea: solve by removing, not adding

What made Hitori stand out, even among Nikoli's inventive catalogue, is its backwards mechanic. Almost every number puzzle of the time, Sudoku included, asked you to fill in empty cells. Hitori did the opposite: it handed you a grid that was already completely full and asked you to shade cells out until no number repeated, unshaded, in any row or column.

That elimination idea is baked right into the name. "Hitori" is Japanese for "alone," short for a phrase meaning "leave me alone," a fitting label for a puzzle about isolating numbers from their duplicates. (We explore the name in full in what does Hitori mean.) Solving by subtraction rather than addition gave Hitori a character all its own and a small but devoted following from the start.

Why it endured

Plenty of clever puzzles are invented and forgotten. Hitori stuck around because it hits a rare sweet spot:

• The rules are tiny. Shade duplicates, keep black cells apart, keep white cells connected. You can learn it in a minute.
• The depth is real. Those three simple rules generate surprisingly deep deductions, especially on larger grids where connectivity and what-if reasoning come into play.
• It feels different. The shade-don't-fill mechanic offers a genuinely distinct experience from the fill-in puzzles that dominate the genre, which keeps it fresh even for seasoned solvers.

That blend of a one-sentence rulebook and surprising depth is the hallmark of a great Nikoli puzzle, and it is what carried Hitori out of the magazine and into the wider world.

A puzzle that travelled

Hitori turned out to travel exceptionally well. Built from numbers and shading rather than language, it needs no translation, and it found enthusiastic audiences far beyond Japan. It became a fixture of international puzzle sites, apps and books, and developed an especially strong following in Europe, where German puzzle communities in particular embraced it. The puzzle's reach is genuinely global, with far more interest worldwide than in any single English-speaking market, a story we tell in why Hitori is so popular around the world.

Along the way it picked up a few regional aliases, including Twincognito and the German "Zahlen streichen" ("cross out numbers"), though the original Japanese name remained the one everyone uses.

Where it stands today

Hitori now sits comfortably in the canon of classic logic puzzles, alongside its Nikoli siblings. It is available on dedicated puzzle sites, in apps, and in puzzle books worldwide, in grid sizes from quick 5×5 starters to demanding 15×15 challenges. Not bad for a humble grid of numbers dreamed up in a 1990 puzzle magazine.

The next chapter of Hitori's history is the one you write every time you shade your way to a solution. Play Hitori now, or learn the rules if you are new to it.

Frequently asked questions

Who invented Hitori?

Hitori was created and popularised by Nikoli, the Japanese puzzle publisher also responsible for popularising Sudoku and many other logic puzzles. It first appeared in Nikoli's magazine, Puzzle Communication Nikoli, in issue #29 in March 1990, built on the company's tradition of handcrafted puzzles with a single logical solution.

When was Hitori created?

Hitori was first published in March 1990, in issue #29 of Puzzle Communication Nikoli. That makes it a modern puzzle from the same era and publisher that later brought Sudoku to global attention.

Why is Hitori different from other Nikoli puzzles?

Hitori stands out for its backwards mechanic. Where most number puzzles, including Sudoku, ask you to fill in empty cells, Hitori gives you a full grid and asks you to shade cells out until no number repeats. Solving by elimination rather than placement gives it a character distinct from its siblings.

Is Hitori a Nikoli puzzle?

Yes. Hitori is a Nikoli puzzle, first published in the company's magazine in 1990. Nikoli is the same Japanese publisher that popularised Sudoku, Kakuro, Nurikabe and Slitherlink, and it handcrafts its puzzles to have a single solution reachable by logic.