Very friendly service and reasonable prices, but the patties are thin and thus are necessarily overcooked. Worth trying if you're close by, but if you're a "thick patty person" who prefers having a burger medium or medium-rare, I wouldn't make a special trip just to sample the grub at Authentic. Try nearby West Park Cafe.
When I lived in HK and the USA, I always felt uncomfortable with Japanese restaurants there because those restaurants usually changed their taste to fit into the local's tongue. I guess Westerners in Tokyo feel the same way. For these guys, I recommend this American style restaurant. Here, you can order the ones you had in your country, although it is a bit pricy. About 1,000-1,500yen for a burger.
Feeling a little homesick? Want something that reminds you of home cooking? Authentic is a terrific little burger joint that reminded me of home. The menu was both in English and Japanese and was fairly basic: burgers, fries and hot dogs. The service was quite good and the food arrived soon after we ordered. I got my burger and it looked delicious. I took my first bite and was delighted that it tasted as good as it looked. There were a lot of toppings and sauce, but the combination was really good. I thoroughly enjoyed my burger and fries and enjoyed the ambiance of the place. It was quite relaxed inside and the lunch atmosphere was enjoyable. We sat at one of the tables in the corner, but there was also a counter facing the kitchen. I would recommend Authentic as a place to go and have a nice burger with a friend or two for both lunch and dinner.