Very tasty food, and the staff speaks enough English to help gaijin like myself order. They know what vegan is, and sometimes have vegan desserts, but not the day I went, sadly.
The vegetable "burger" is not what you'd expect, as it has no patty, it's just grilled vegetables on a bun with your choice of spreads. However, it was very tasty so I wasn't disappointed.
Definitely recommended for vegans in Japan.