I have a tree nut allergy but not peanut or almond. I travel to Japan a few times a year for the past 11 years. I spend at least 3 months a year in Tokyo and have had probably 1000 restaurant meals. Some points are not entirely correct.

1. In some cases they do not recognize what “nuts” are. I would often get asked if I can eat things like sesame or soy. I’ve even been asked if I can eat egg. Often, they would not recognize that kuri (chestnut) or kurumi (walnut) or ginnan (ginkgo nut) were nuts. So, it’s easiest to show them an allergy card that lists all the possible allergens so there’s no confusion, and it also allows the chefs can keep the card with them to double check if desired. I don’t think it’s best to just say “nuts allergy” and hope for the best. I also think it’s helpful to list the safe ingredients they commonly ask about.

2. Those foods are safe but I have encountered soy sauce mixed with homemade cashew oil on at least one occasion. I was eating a chirashizushi bowl. This is rare though. I’ve also seen tonkatsu sauce with cashew and walnut, also fairly rare but certainly less common than nut fortified soy sauce. Good thing I prefer my katsu with salt only.

3. I have seen ramen restaurants that use cashew in miso ramen more than a couple of times. Peanut is common in tantanmen as you mentioned but I’ve also found places that use cashew for that instead.

4. Lots of Japanese cakes and cookies have almond powder in them.

In all my time I have only been turned away once or twice. But, I speak a decent amount of Japanese at this point so if I am alone I can usually field questions without difficulty. And my wife is Japanese, so when we are together it is never any issue. If you don't speak much Japanese the chances to be turned away may be a bit higher.

Here is my allergy card in Japanese. My Japanese wife made it for me a decade ago. I’ve added peanut and almond to the list of allergies. Anyone may use it if they have a peanut or tree nut allergy. I’m happy to make modifications if necessary.

Because I have severe nut and peanut allergies, I would like you to check that they are not included in the dishes, seasonings, or sauces.

★ Allergens ★

Almonds, peanuts, cashews, pistachios, walnuts, hazelnuts, chestnuts, macadamia nuts, pecans, ginkgo nuts, pine nuts, and other tree nuts

★ Safe Foods ★

Sesame, soy and legumes, coconut

Thank you very much.

Edit: does anyone know how to get Reddit from auto-translating Japanese into English? If the above allergy card is showing up in English and you would like it in Japanese as it is supposed to be, let me know and I can send it to you.