See here for a comprehensive list of types of fish.

*The word Ekisu (extract) is found after the animal products listed above in a surprisingly large range of product ingredients. I've found meat extracts listed on plain potato chip packs! It's possible that some of the "extracts" are not extracts at all but artificial flavours, but there is often no way to be sure. Of course, the word ekisu isn't always a warning sign, as it's also found after a lot of non-animal food such as;
shiitake 椎茸, しいたけ, シイタケ
konbu (kelp seaweed) 昆布, こんぶ
yasai (vegetable) 野菜
gārikku, ninniku (garlic) ガーリック, ニンニク
daizu (soy) 大豆
onion オニオン

*Katsuobushi (dried bonito) is one of the biggest nightmares for vegetarians and vegans in Japan. Katsuobushi, or katsuoekisu (bonito extract) turns up in soups, sauces, dressings and all kinds of products. Katsuobushi is also sprinkled on salads, tofu, okonomiyaki and other things when you don't expect it.

*Bacon and ham turns up in a lot of unexpected places, particulary pasta, salad and bread products. The menu often won't mention that bacon is contained in the dish so you often need to ask.

*Jako and Shirasu are tiny fish often used as seasoning and people often forgot that vegetarians cannot eat them. Watch out for thousands of tiny eyes looking at you from salads, pasta, tofu, hijiki and hidden in unexpected places.

*Lard is sometimes added to bread in Japanese bakeries, so check the ingredients or ask. Some old izakayas still cook with lard instead of vegetable oil.

*Shortening is commonly found in bread products, cakes, desserts, cookies and sweets. Unfortunately, the source of the shortening is almost never mentioned. Shortening is often made with butter, lard, margarine or hydrogenated vegetable oil. Even if vegetarian, it is well known that trans fats are harmful to our health.

*Gelatine turns up in desserts, yoghurt etc as it does in every country. Though, one good thing in Japan is that sometimes kanten (made from seaweed) or konnyaku (made from a kind of yam) is used to make things gelatinous.