Any kind of dietary restrictions in a foreign country can be a bit unnerving. Knowing what to look for in lists of ingredients (or learning how to ask for specifics) can be incredibly helpful.
The first time I went to Japan, I had absolutely zero restrictions and I ate to my heart’s content, no matter what was offered to me. I’ll admit, my palette will truly miss the blessed flavor of Osaka’s own takoyaki, but hey, I’ll get over it (already am).

One of the great things about Japan is the abundance of soymilk. In fact, when I went (and was a dairy milk fiend) I had a harder time finding dairy milk because soy was every where.
The kanji for soy will look like this: 豆乳 (tounyuu, pronounced tone-you). Now to be fair, not all soymilk in Japan is vegan. There are plenty that have additives in them. Not all of these additives will be animal derived, but sometimes they are. Basically your only 100% bet is to call the company and ask them. There is a non-adjusted soymilk that won’t contain these additives. The kanji for it is quite a mouthful (no way that I remember it off the top of my head), so I’ll paste it here in case it is something you want to look for. 無調整豆乳 (which I believe is read as muchousei tounyuu, pronounced moo-cho-say tone-you).
Calcium lactate is an additive to watch out for. The kanji/kana for it will look like this: 乳酸カルシウム (nyuusan karushiumu, pronounced niew-sahn kah-roo-she-oo-moo). Once again, just because it’s labeled with this does not necessarily mean it isn’t vegan, it’s one of those things that vary by company.
Last I heard, Kikkoman brands do not contain any milk product in their soy drinks (coffee included!), and Kikkoman is clearly labeled on their packaging, in the roman alphabet, so it’s easy to spot. I lived on Kikkoman coffee my first three days in Japan until I became brave enough to start asking the sales clerk more questions.

Soy yogurt is also available in Japan, but watch out for gelatin. Why must we add gelatin in everything? Please beware of Soyafarm yogurt. I ate at least three of these and found out it contains gelatin.
Gelatin will be labeled in katakana, rather than kanji and the little bastard looks like this:  ゼラチン (zerachin, pronounced jeh-rah-chin. That “j” is very soft, think “zsa zsa”).

You will also find almond milk here and there, and it’s much easier to identify as it almost always has almonds on the packaging. It’s usually written in katakana on the front of the package and looks like this: アーモンド (aamondo, pronounced aah-mon-doe). If you want to be sure it’s almond milk, you can always walk up to one of the workers while holding up the drink and say “Sumimasen, kore wa aamondo miruku desu ka?” And if the reply is “hai, aamondo miruku”, or just a simple “hai”, then you are in luck. But honestly, all of the almond milk I encountered had pictures of almonds on the packaging.

Moving onto bread… Oh, how unfortunate, most bread in Japan contains milk and eggs. Really, it’s hard to find bread without milk and eggs. Your best bet is probably going to a bakery and explaining you can’t consume dairy (or animal products, for that matter, because some contain lard!). If you want to ask if it contains dairy or lard, you can ask this:
“Kore wa raado ga haitte imasu ka?” or dairy “Kore wa nyuuseihin ga haitte imasu ka?” (Side note, you can use this phrase for any inquiry that a product might contain. Just replace the italicized word with the word that you are specifically asking about.)
You’re usually safe with sweet potato breads and imported breads (that have English labels and you can check for yourself). Unfortunately, it is very hard to find vegan bread in Japan.

Rice is usually safe, in my experience, though some do contain collagen. It will be written in the ingredients in katakana like this: コラーゲン (coraajen, pronounced koh-raah-jen). Other than that, it should be okay.

Next time I go to Japan, I will try to be more mindful of taking photos of ingredient lists so I can update this post here, giving you a better idea of what to look for.

Any go-to vegan products in Japan that are your favorites?