Kurosaki Kokusen AS Santoku 170mm - Curly Maple

Both are all-purpose Japanese knives, and for most home cooks either will handle the bulk of daily prep. The choice comes down to length, blade shape, and how you like to cut.

A gyuto is the Japanese chef's knife, with a gently curved edge that lets you rock and slide through cuts as well as chop. Tojiro's guide to Western knife shapes gives 150 to 210mm as the household size for a gyuto and up to 360mm for professional use. The extra length and pointed tip give you reach and versatility, from proteins to large produce.

Tojiro's guide to Japanese knife shapes gives 165 to 170mm as the household size for a santoku, which has a flatter profile and a rounded sheep's-foot tip. It rewards a straight up-and-down push cut, feels nimble in smaller hands or tight kitchens, and is the classic Japanese household knife.

Rule of thumb: choose a gyuto if you want one do-everything knife with more reach, or a santoku if you prefer a compact, easy-to-control blade. Plenty of our customers end up owning both.

Match the shape to your stroke. Rock chopping keeps the tip on the board and rolls the curved belly through the food, so a gyuto or a Western chef's knife suits it, and Japanese knives rock fine as long as you rock gently.

Up-and-down chopping, the Chinese style, wants a straight run of edge, so a nakiri, usuba, santoku or bunka suits it better; a curved edge chopped straight down easily leaves pieces joined. Neither shape is better; it depends on how you cut.

A Japanese dictionary explains the name of the santoku (三徳包丁) as coming from the three things it handles: meat, fish and vegetables. The same dictionary entry points from the santoku to the bunka (文化包丁), treating the two as one knife.

One Japanese knife maker guide distinguishes the two by the tip. It says that in the Showa era the bunka was made with its tip cut at an angle, and the santoku came after it by rounding that tip.

Yes, carbon steels such as Aogami (Blue) and Shirogami (White) react with food, moisture, and acids, so left wet they can spot or rust. With normal use they develop a grey, blue and brown patina, and that patina is expected on a carbon knife rather than damage.

Aogami has only a little chromium, far below what a stainless steel needs, so water left sitting on the blade will spot it. A patina is a stable oxide layer that slows rust down; orange or red specks are rust.

Care is simple once it becomes habit:

• Wipe the blade as you go, especially after onion, citrus or tomato.
• When you finish, wash it in warm water with a little soap and dry it straight away with a towel. Don't let it air dry or leave it in the sink or the dish rack, and never put it in the dishwasher.
• Store it dry: on a magnetic strip, in a saya or in a block in a dry spot.
• If it's going to sit unused for a while, wipe on a thin film of food-safe mineral oil before storing it.

If you do find rust, lift light orange spots with a rust eraser and a little water, then dry and oil the blade. We stock the CKK and Naniwa rust erasers, and the Koyo Sunlite Polishing Paste (Blue for Steel) lifts light surface rust or refreshes a finish. Rust on the edge itself comes off the next time you sharpen. Deep pitting needs a professional sharpener. Avoid steel wool and harsh scouring on a polished or kurouchi finish, because they scratch it.

On a stainless-clad knife only the thin line of carbon steel along the edge can rust; the cladding stays clean. A carbon-clad or honyaki blade can rust over its whole face and needs the same care all over.

Carbon steel rewards this small amount of attention with a keener edge and easier sharpening than most stainless.

Aogami Blue steel, specifically Aogami Super (Blue Super), is a high-carbon Japanese knife steel made by Proterial that chefs value for its ability to take an extremely sharp edge and hold it longer than most other carbon steels, thanks to a composition with 1.40 to 1.50% carbon, 2.00 to 2.50% tungsten and 0.30 to 0.50% vanadium.

The "Blue" in Aogami refers to the color of the paper the steel is wrapped in at the mill, not the steel itself. Proterial describes Aogami Super as an alloy steel with tungsten, chromium and vanadium to improve heat-treatment properties and wear resistance. Proterial gives it a hardening hardness of over 60 HRC, giving you a blade that can be ground very thin for aggressive cutting performance while still resisting chipping in normal use. The trade-off is that, like all high-carbon steels, it is not stainless: it will rust if left wet or acidic, so you need to wipe it down and keep it dry.

Aogami (Blue) steel has less than half a percent of chromium, nowhere near what a stainless steel needs, so water left sitting on the blade will spot it. Dry it as soon as you finish, keep it somewhere dry, and let a patina build. Do that and aogami will hardly ever rust. On a stainless-clad knife only the thin line of aogami along the edge can rust; the cladding stays clean.

Will a carbon steel knife rust? covers patina, rust removal and which cladding rusts.

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.

Yes, Yu Kurosaki is widely regarded as one of the leading Japanese knife makers of his generation, known for combining exceptional cutting performance with artistic, hand-forged designs. Based in Takefu, he established his own workshop in 2014 after twelve years at Kanehiro Uchihamono (カネ弘打刃物), and he was certified as a traditional craftsman (伝統工芸士) in 2019. His knives are built around thin geometry and advanced steels like SG2 and Blue Super, which contribute to strong edge retention and precise cutting. He is also celebrated for innovative finishes such as Tsuchime and Suminagashi, which set his work apart visually while maintaining traditional craftsmanship.

Kurosaki's reputation is built on a clear philosophy: aiming for the ultimate knife. He is known for his use of SG2 and Blue Super steels, paired with distinctive hammered and layered finishes, which together deliver a balance of strength, edge retention, and aesthetic originality. For a closer look at his work and approach, you can explore the Yu Kurosaki maker page on the Knives and Stones site.