Japanese kitchen knife steel, explained by the numbers on the page

Chubo's own summary is the place to start: Japanese blades 'are generally harder and forged thinner by skilled blacksmiths. This results in better edge retention and precise cutting performance', and the steeper edge angles are why cooks call them 'lasers'³. The two numbers that matter on a product page are the steel and the Rockwell hardness. Steel decides whether the blade stains: a stainless or clad blade can be wiped and left; a carbon blade must be dried at once and oiled before storage². Hardness is a maker's figure for how hard the heat-treated steel is: Chubo calls its HAP40 line, at 65 to 66, the knives that 'hold an edge better than any knife on our site' and says that 'despite their incredible hardness, they are very responsive to sharpening stones'¹.

The names on Chubo's filters group like this. VG10 is a stainless core steel Chubo sells clad in damascus (Sakai Takayuki 33 Layer, 60 HRC) or stain-resistant steel (Tojiro DP, 60 HRC)¹. R2 is a powdered stainless steel; Takamura's R2 santoku is 62 to 63 HRC with a 1.6 mm spine¹. Ginsan ('silver 3') is a stainless Chubo describes as 'a tough steel with excellent edge retention and easy maintenance', 61 HRC on the Kazan¹. SLD on the Kazan Wa-Gyutou is 60 to 62 HRC¹. HAP40 is a powdered 'semi-stainless' blend with vanadium, molybdenum, cobalt and tungsten, 65 to 66 HRC¹. White #1 (Shirogami) and Blue #2 and Aogami #1 are carbon steels; Matsubara's Blue #2 is clad 'in the san mai style for stain-resistance and ease of sharpening' and is 62 HRC, while the hand-forged Akira-Saku White #1 is 59 HRC with a 4 mm spine². Misono's UX10 is a 'sub-zero treated Swedish steel' at 59 to 60, and its Swedish Carbon line a 'purest carbon steel' at 60¹².

Every carbon knife page on Chubo carries the same warning: 'This knife is made from carbon steel, which gets incredibly sharp and is easy to sharpen but requires additional maintenance. This knife should be kept clean and dry at all times and oiled when not in use for an extended amount of time. Carbon knives can be reactive with high acid foods.' The Akira-Saku page adds, under its care tab, 'Carbon steel is not stain resistant. Wipe completely dry after use.'²

What you will see is a patina. Chubo's guide defines it as 'a thin layer of oxidation that forms when carbon steel reacts with oxygen, moisture, and acidic foods', which 'is generally stable and can help protect the blade's surface', and separates it from rust, 'active corrosion' that 'commonly appears orange or reddish-brown and may feel rough, flaky, powdery, or raised'. A patina 'does not make a carbon steel knife rust-proof'⁴. The maintenance list is short: hand wash with mild soap, dry immediately and thoroughly, wipe the blade during use on wet or acidic foods, store dry, oil with food-safe mineral oil before long storage; avoid dishwashers, prolonged soaking, harsh scrubbers and damp storage⁴.

Two of the carbon knives on Chubo are clad to soften that routine: the Matsubara Blue #2 has a softer steel over its core 'for stain-resistance and ease of sharpening and maintenance', and the Karaku's kurouchi finish 'offers protection from discoloration'². The edge itself is still carbon and still wants drying.

Chubo ships from its Japan warehouse by FedEx International Priority, 'Monday through Friday', arriving 'in 4 to 5 business days from the shipment date'. For the US and Canada: 'We offer free shipping on orders over $200 USD. For orders under $100, the shipping fee is $25. For orders of $100-$200 the shipping fee is $15.' Since August 2025 US orders ship 'DDP (Delivery Duty Paid) so you will not receive any additional charges at delivery'⁵. On the table above, that puts the $109 Tojiro at $124 delivered and the $194 Takamura at $209 by our arithmetic, while the $198 Kazan Ginsan crosses the free-shipping line with a $5 stone or saya in the cart.

Returns: 'Returns are accepted within 15 days of delivery as long as the returned items are in their original condition and original packaging.' Refunds cover the purchase price; 'shipping and handling fees are non-refundable', and 'Returns will not be accepted without a return authorization number', requested by email before shipping. Damage in transit must be reported 'within 48 hours of delivery'⁵.