Masakage Koishi AS Sujihiki 270mm, K&S Hearted-shaped Ironwood Handle

Between 210 and 270 mm, depending on where it will work. One Japanese maker lists 210 to 240 mm, double-bevel, for home use and 240 to 270 mm, single- or double-bevel, for professional kitchens.

Another, in Sakai, recommends 240 mm at home, with the size of your board in mind, and 270 mm for professional use.

A sujihiki is a long, double-bevel knife for dividing larger pieces of meat into their parts, and its length lets it slice sashimi too; a yanagiba is the sashimi knife.

The Sakai cutlery association describes the yanagiba (柳刃包丁) edge as so acute that it cannot be used on bone or other hard things, so choose the sujihiki for meat and the yanagiba if sashimi is the main job.

Yes, carbon steels such as Aogami (Blue) and Shirogami (White) are not stainless steels, so left wet they can spot or rust.

Care is simple once it becomes habit. Wipe the blade as you go, especially after acidic food like citrus, tomato or onion. When you finish, wash it in warm water with a little soap and dry it straight away with a towel. Do not let it air dry, leave it in the sink or the dish rack, or put it in the dishwasher. Store it dry: on a magnetic strip, in a saya or in a block in a dry spot.

If the knife will sit unused for a while, wipe on a thin layer of oil before storing. In our video James shows that mineral oil can stand in for camellia (tsubaki) oil, and he picks one labelled medical grade; we list the Kitchen Knife / Cutting Board Mineral Oil Medical Grade for this. If you find light rust, lift it with a rust eraser and a little water, then dry and oil the blade; we list the CKK and Naniwa rust erasers.

Aogami Super, also called Blue Super, is a knife steel made by Proterial. Proterial describes it as an alloy steel with tungsten, chromium and vanadium, to improve heat-treatment properties and wear resistance. Its own figures put carbon at 1.40 to 1.50%, tungsten at 2.00 to 2.50%, vanadium at 0.30 to 0.50% and chromium at 0.30 to 0.50%.

Proterial gives it a hardening hardness of 60 HRC or more. The uses it lists for the grade are high quality planes, other tipped tools, kitchen knives and sickles. Proterial's hardening note calls for quenching in water, with oil as the alternative.

It is a carbon steel, not a stainless one. Wipe it dry after use, do not leave it wet or in the sink, and do not leave acidic food on it.

Aogami (Blue) steels are carbon and alloy steels, not stainless, so water left sitting on the blade will spot it. Each Aogami grade lists only a little chromium, between 0.20 and 0.50% depending on the grade, and that is not enough to make the steel stainless.

Dry the blade as soon as you finish cooking and after washing, and store it somewhere dry. Lift any rust early.

Will a carbon steel knife rust? covers rust removal and everyday care.

The difference is in Proterial's own figures: Aogami Super has 1.40 to 1.50% carbon, 2.00 to 2.50% tungsten, 0.30 to 0.50% chromium and 0.30 to 0.50% vanadium, against Aogami 2 (Blue 2) at 1.05 to 1.15% carbon, 1.00 to 1.50% tungsten and 0.20 to 0.50% chromium.

Proterial describes both as alloy steels with tungsten and chromium to improve heat-treatment properties and wear resistance, and also names vanadium for Aogami Super. Both pages list hardening hardness over 60 HRC, and Proterial lists Aogami Super for high-quality planes, other tipped tools, kitchen knives and sickles.

Masakage is a brand, not a single forge. Takayuki Shibata (柴田 崇行) dates it on his own site to 2008, as his first brand, and gives his reason: "Smiths were retiring and dying, and no one was replacing them. I felt that I had to make my own brand."

The same site says he took up sharpening in 2007, taught by a local cutler, and put bigger orders in to his blacksmiths as sales grew. Shibata's company is Iron Clad, in Fukuyama, Hiroshima.