Kyoto is genuinely one of the better cities in Japan for vegetarian and vegan travellers, largely thanks to its deep shōjin ryōri tradition — but it takes a bit of knowledge to navigate well, since Japanese cooking uses fish-derived stock far more pervasively than it first appears.
The dashi problem
Traditional dashi — the stock base underlying an enormous amount of Japanese cooking, including miso soup, many simmered dishes, and sauces that don't read as "fish dishes" at all — is very often made with katsuobushi (bonito flakes). A dish can look, and be marketed as, vegetarian while still containing fish-derived stock. This is the single biggest thing to watch for, more than any obviously meat-based dish.
Shōjin ryōri: the reliable option
Because shōjin ryōri is built specifically around Buddhist dietary rules, it's the most dependable category for genuinely meat- and fish-free eating in the city — see our shōjin ryōri guide. It isn't automatically vegan, though: some preparations use dashi made from kelp and dried mushroom rather than being strictly plant-only in every ingredient, so it's still worth confirming specifics for a fully vegan diet.
Useful phrases
Explaining dietary restrictions in Japanese helps enormously, even with limited language ability — a translation app with a written note explaining "no meat, no fish, no fish stock" (胉も魚も魚のだしも使わないでください) tends to communicate the dashi issue specifically, which a simple "vegetarian" claim often doesn't.
What travels well
Tofu and yuba dishes, most vegetable-forward Nishiki Market stalls (though check individual items), and dedicated vegan/vegetarian cafes — an increasingly visible category in central Kyoto — are generally safe, reliable choices. Convenience store options are more hit-or-miss and worth checking labels on, though awareness has improved substantially in recent years.