This is an Izakaya which is like a kind of Japanese bar, typical in Japan, where you can drink and have different small plates of food. This kind of bar normally offers different kinds of alcohol. I would say that this one is quite authentic. The foods are authentically tasty (though they're not super special, just like typical Japanese food in Japan). I ordered a typical Japanese drink called Umeshu. It's not easy to find it here in Valencia, except if you go to a big Chinese supermarket. They've also got Japanese sake, but this one is not very special because many other Japanese/Chinese places also offer the same kind.
I talked to a Japanese guy who is working there, so to me it's a guarantee that it's an authentic Japanese place (because many of Japanese restaurants here are run by Chinese and they're not very authentic).
The service is pleasant, though it's not special. The atmosphere is nice. It's a small place and always packed. Most of the time you have to make a reservation and it goes by 2 rounds in the evening: from 20:30 and from 22:00 (if I'm not wrong). read more