JasCruz wrote:wow, thank you so so much! you've been extremely helpful
Incidentally, to make sure that I'm not inadvertantly going to kill your boyfriend, I did a google search for "Japanese food nuts", and it appears as if some Japanese food contains ginkgo nuts. (銀杏, "ginnan" in Japanese) It's unlikely that Japanese people would consider these to be "nuts", which is basically a catch-all term for "foreign nuts". Apparently, they often appear in chawanmushi (茶碗蒸し), which is a kind of egg custard.
I have absolutely no idea if people with allergies to peanuts, etc. are also allergic to ginkgo nuts, but it's something to keep in mind. I sincerely doubt you'll come across many ginkgo nuts in your time there though.
There's also "marron" (マロン), which means "chestnut", and usually assumes the form of a disgusting sweet paste. You'll mainly see it as a doughnut topping at Mister Donut. You'll want to avoid this regardless of allergies.