This place is the best. I felt at home here. Some background: the owners are a husband/wife team that grew tired of the harder texture traditional okonomiyaki had because it is usually made with wheat, so they got rid of wheat flour and created their own recipe devoid of wheat -- they use rice flour instead. The only possibility for gluten to be introduced is through added herbs/spices, and they add that separately. Everything else is naturally GF. DF is also a possibility. There are so many options for food and there is an easy-to-follow card that is given when seated asking to identify any preferences or food allergies (in both English and Japanese). Both of the owners are amazingly sweet and welcoming, and both speak conversational English. I had no problem interacting with them when we spoke at length. Fun fact: the husband is a former record label engineer who now helps with the business and made every plate or bowl you'll eat from (seriously some of the most beautiful pieces I've ever seen).
I had a great GF okonomiyaki here. The owners don't speak much English, but they have a visual board were you can point out your allergies and they take them very seriously. I went with a friend that speaks Japanese so I was able to ask questions about their ingredients. They even have GF okonomiyaki sauce! (the owner even showed me the GF soy sauce he uses when cooking)