This is where most people get tripped up. Wagyu refers to a breed, whereas kokusan-gyu, or domestic beef, means any cattle raised in Japan, including imported breeds. The labels look alike, which is exactly why the distinction matters.
Only four breeds may be labelled wagyu: Japanese Black, Japanese Brown (Akage), Japanese Shorthorn and Japanese Polled, or crosses between them. Any other breed, however long it has been raised in Japan, cannot legally be called wagyu.
Kokusan-gyu means cattle raised in Japan for at least a set period. Breed is irrelevant, so the term covers everything from Holstein dairy cattle and F1 crosses (dairy breed x wagyu) to American and Australian stock finished in Japan. It is far cheaper than wagyu.
F1 is a cross between a dairy breed and wagyu, usually Japanese Black. It keeps something of wagyu’s flavour while keeping rearing costs down, and family restaurants and everyday yakiniku places sometimes list it as "Kuroge wagyu" — which is legal.
A menu that says "made with Kuroge wagyu" does not guarantee that every piece of meat on the plate is Kuroge wagyu. What you want to see is a formal designation such as "100% Kuroge wagyu", "Matsusaka beef" or "Kobe beef". That is the mark of wagyu you can trust.
Wagyu: 1,500-15,000 yen per 100g, depending on cut and brand. Domestic beef (dairy breed): 300-800 yen per 100g. F1: 500-1,500 yen per 100g. Imported beef: 200-600 yen per 100g. The gaps come down to breed and how the animal was raised.
The right approach is to match the beef to the occasion. A special day: wagyu, such as Matsusaka, Kobe or Omi. Everyday meals: domestic beef or F1. On a budget: imported beef. Each has its own merits, so choose according to the moment.
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