The santoku is sold as the knife for meat, fish and vegetables, so it is fair to ask why a Japanese kitchen would also need a deba. Tojiro, a knife maker in Niigata, has a Japanese guide to the santoku in which it breaks down a horse mackerel with one and lists what the knife could and could not do. I read that guide next to the deba page of a Sakai knife shop and the listed weights of two knives that cost almost the same.
If you only want my pick for a first deba: the Sakai Takayuki Kasumitogi white steel deba 150mm, $114.99 and in stock when I checked on 7 October 2026. It is carbon steel and needs drying. If you do not own a santoku yet, buy that first, and the reason is below.
What the santoku managed
Tojiro writes that with a small horse mackerel, taking the head off and filleting it into three pieces is possible with a santoku. It then names two steps where the result was less precise than with a single-edged deba: removing the row of hard scales near the tail, and lifting the flesh off along the bones.
The explanation it gives is about the grind. A santoku is sharpened on both sides. Tojiro says a double-edged blade is less stable when it is run along bone and tends to shave into the flesh, so the cook has to control the angle more carefully than with a single-edged knife. Under the heading for what beginners tend to notice, it writes that the santoku will cut, but the work is awkward.
It adds one more point about fish. A santoku can slice sashimi off a block, but the blade is too short to finish the slice in one pull, and Tojiro says the texture suffers.
Putting those together, a santoku is fine with fish that is already filleted and can get through a small whole fish if it has to, but it is at its weakest along the bones, and that is the part of the job a deba is made for.
What the deba is built for
Sakai Ichimonji Mitsuhide, a knife shop in Sakai, describes the deba as very thick and wide even among Japanese knives and heavy in the hand, and says this is so the blade does not lose against the hard bones and heads of fish.
The listed weights show how far apart the two knives are. On Hocho-Knife the Sakai Takayuki INOX PRO santoku with a 180mm blade is 160g. The Sakai Takayuki white steel deba with a 150mm blade is 230g. The deba is 30mm shorter and 70g heavier, and the two cost $117.99 and $114.99 on 20 October 2026.
The deba is also sharpened on one side only. One face is close to flat, and that face rides along the backbone while the fillet comes away. This is the stability Tojiro found missing in the santoku.
What a deba is bad at
Neither source presents the deba as a general kitchen knife. Tojiro makes the division plain in its guide to all-purpose knives: the nakiri is for vegetables, the petty knife for peeling and small work, the deba for breaking down fish, and the santoku for when you want one knife to cover everything. A blade that thick and that heavy is made for one job, and I would not expect it to be pleasant on an onion.
Going the other way, I would keep a santoku off fish heads and heavy bones. Tojiro only tried it on a small horse mackerel, and at 160g it is a much lighter blade than the knife made for that work. What Japanese makers say about chipped edges is in my Japanese knife chipped.
The santoku is the newer knife
Ichimonji writes that the nakiri and the funayuki, a lighter relative of the deba, used to be the main knives in Japanese homes, so a household had one knife for vegetables and one for fish. The santoku arrived later and took over the work of the vegetable knife and most of the rest. I covered that history in nakiri vs santoku.
Going by what Tojiro found, the whole fish is the part the santoku did not fully take over. Ichimonji still lists a home size for the deba, 150 to 165mm, alongside the professional ones.
Which one to buy
If you own neither, buy the santoku. It handles vegetables, boneless meat and filleted fish, and Ichimonji calls it popular as a first knife for the home because it has no weak point.
Add a deba if you bring home whole fish more than now and then. Ichimonji treats 180 to 210mm as a professional size. Tojiro gives similar numbers, 150mm for small fish and 180 to 210mm for medium and large ones.
If your fish comes filleted, a santoku is enough and you can leave the deba out.
If you already fillet with a Western flexible knife and are wondering whether to switch, I compared those in deba vs fillet knife.
Left-handed cooks should check the price before deciding. A santoku works in either hand, but a deba is ground for one hand, and the left-handed version of the white steel deba below is $207.99 against $114.99. The reason is in single bevel vs double bevel.
Three knives, checked on 7 October 2026
The santoku: the Sakai Takayuki INOX PRO santoku 180mm at $117.99. 160g, stainless with a stainless handle, double-edged for either hand, in stock.
A first deba: the Sakai Takayuki Kasumitogi white steel deba 150mm at $114.99. 230g, single-edged for the right hand, in stock. White steel rusts if left wet, so wipe it while you work. What to expect is in patina or rust.
The stainless deba: the Sakai Takayuki INOX ai-deba 150mm at $167.99. 230g, AUS8A stainless with a magnolia handle, single-edged for the right hand, in stock. It costs 53 dollars more and removes the rust question.
Disclosure
I have four approved affiliate partnerships: two with knife retailers, Hocho-Knife and SharpEdge, and two with Japanese language-learning companies unrelated to knives. This page carries four tracked links, all to Hocho-Knife: three knives, and a second link to the white steel deba near the top. At about 10 percent, that is roughly 12 dollars for the santoku, 11 dollars for the white steel deba and 17 dollars for the stainless one. The santoku I tell you to buy first and the deba pay me about the same. Tojiro is quoted here as a source, and this page does not link to any Tojiro product. My full affiliate disclosure is here.
Sources, checked on 7 October 2026: the Japanese guides to the santoku, to all-purpose knives and to knives for breaking down fish published by Tojiro; the Japanese santoku and deba pages of Sakai Ichimonji Mitsuhide; and the Hocho-Knife product pages for the knives named above.