Funny thing is, The minute I signed my contract to work in Tokyo for the Olympics, I googled, "What to eat in Tokyo when you hate seafood"
My wife and I had our honeymoon in Okinawa....went out to lunch and for two bowls of miso soup, a pot of tea and a couple pieces of sushi the bill was a hundred bucks US....let's say overeating isn't a problem in Japan...they have McDonald's over there..you'll be fine
Add a couple, just a couple, nothing more, of drops of hot sauce to your canned tuna. It won't make it hot or spicy but really enhances the flavor of the tuna. You'll thank me later.
Loathe mayonnaise. Sometimes make tuna salad that's real salad, half tuna, half vegetables with yogurt sauce. Yogurt by itself is too dry but I make yogurt sauce with olive oil. Best ways fresh tuna nicoise or seared medium rare.
Mayo, a little horseradish, dill pickle relish, pepper and garlic salt. Then I eat it with tortilla chips.......
Straight up catching a tuna then eating it raw is something everyone should do. Out of the can I usually add some mayo, brown mustard, spices. Then eat it with pretzels. A tuna melt is the real OG move though.
Tuna salad for me is: Tuna, diced sweet onion, diced celery, zucchini relish (or regular if that's all you have), shredded sharp cheddar, salt, pepper, garlic powder, mayo, and honey mustard.
Although sometimes, I switch things up and use: Tuna, sesame oil, honey, garlic aioli, splash of Tamari, splash of Mirin, fresh chopped onion greens.