The real question of course, is which knife, or knives should you buy.
For a moment, forget that you're the world's greatest Sushi chef and you want a knife to use in your western kitchen.

Real domestic Japanese knives are one sided and usually meant for a specific purpose, which isn't always compatible with the normal sort of cutting that an Australian chef (home or professional) will need a knife for.

When WAS the last time you broke down a complete blue-fin tuna?

Knife Styles?
See our range of knives here.

Nenox G series Gyuto Japanese knife
Misono Molybdenum Santoku 180mm
Akifusa Powder Nakiri knife 180mm
So, after all that, which knife/knives should you buy?

General cooking - Gyuto, Nakiri & Petty. These will handle most slicing, including great vegetable slicing and smaller jobs.
General & slicing - Gyuto, Sujihiki and Petty. Biased towards slicing fish and meat as well as general use, with meat cutting and herbs.
General and bones - Santoku, Petty and a Cleaver for chopping through chicken bones and fish.

Just a pair?

Gyuto and Petty
Santoku & Petty

The ultimate choice is yours of course, as only you know your particular style.

Very important:

There is no use in buying a Ferrari if you're going to take it on rough roads.

Knives need to be cared for and treated properly and to a large extent, that means learning to use them properly. If you are directly chopping down as fast as you can with a Gyuto, and it sounds like a machine gun, your knife WILL go dull quicker, as the blade edge is bent over from the impact with the cutting surface. This will, of course happen sooner on a European knife, but why do it anyway?

The correct way to use a Gyuto, is to have the tip on the board and to slice through the food in a forward or rearward motion, (whichever suits you) which entails the end of the blade contacting the cutting surface at the end of the cut with hardly a noise. Use the Petty the same way.

With the Nakiri and Santoku, the motion is like landing a plane, as the blade cuts forward and down and gently contacts the cutting surface along most of the blade edge surface.

The best use of knives, is to use the cutting edge to cut the meat or vegetable only and NOT forcibly stopped by the cutting surface. Sounds pretentious, but using great knives is like dancing the ballet - hard to learn, but amazing to watch when it's done properly.
Gyuto  - This is the Japanese equivalent of the classic French chef's knife used in Europe and Australia for the last 2 hundred years at least. A close enough translation of the name is "Cow Sword", which gives you a fair idea of its intended use. It is useful for all general slicing and cutting tasks, but you will find that because of its slimmer blade, it cuts more easily and the extra hardness of the blade steel, will mean that the edge remains sharp for a lot longer than Euopean knives. See our comparison of the profiles of Japanese and European knives. You'll find the gyuto is the smoothest transition from the European knife to the Japanese style.

Santoku - This blade name literally means "three virtues" - Slicing, Dicing & Mincing, with a slight vegetable bias. Usually found in lengths of 160 - 190mm. They are becoming more popular because of their smaller and easier to handle size and their unique shape. At the moment, the most popular knife in Japan.
Nakiri - The nakiri is a vegetable knife and is under-used in the western kitchen. The shape enables the blade to contact the cutting board squarely after your cut and ensure that the vegetable has been cut completely, without the annoying connection you sometimes find with the Gyuto. These knives cut onions to perfection. Vegetarian's ideal knife.
Ohishi Tsuchime Sujihiki 240mm
Sujihiki - "Flesh Slicer". just what the name suggests - it slices beef, turkey, raw meats and fish. Longer and narrower than the Gyuto, for less resistance when slicing.
Tojiro Traditional Deba Knife 165 mm
Deba - Heavier and shorter knife than the gyuto, for filleting fish -  and butchery with boneless meat. Nimble and precise, despite the heavier construction.
Deba come in 2 types
Western -
50/50 profile, sharpened on both sides
Japanese  -  Single sided 100/00  - more efficient.
Tanaka Ironwood knife at Japanese Chef
Petty/utility - A smaller version of the Gyuto, 120 - 150mm in length, for the smaller cutting jobs, like slicing shallots and herbs and boning smaller cuts of meat, fish, or birds. Becoming more popular as a complementary knife to the gytuo, or santoku.
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Fine Japanese chef's knives to Australia since 2007