During our holiday in Japan, my wife and I wanted to try good japanese vegetarian food, but were afraid of secret meat and dashi, especially in noodle-dishes. But the Asahi served really good Soba-Noodle-dishes, without using dashi and mostly (one exception) vegan.
The owner was very nice, although he just spoke little english, he tried his best to explain every menue - and with his efforts and our little japanese we came along well. He had a small handwritten menu-card in english, too.
The place is very small, but it has a cozy atmosphere. It is easy to find from the Higashikitazawa station on the Odakyo local train.
Every dish we tried was delicious, especially the soba in the red soup with cucumber (I forgot the name), and we were even served some sides for free (for example Yudofu).
I would definitely recommend this place to every vegan/vegetarian visiting Tokyo!