There are many reputed Kobe beef venues in Tokyo, although if you read extensively very few are actually Kobe, but rather similar types of cow bred elsewhere. In order to be designated Kobe beef, the specific black Tajima-ushi cow breed that is born, raised and slaughtered in Kobe. It seems that only a few Tokyo restaurants serve authentic Kobe beef, which may be imported beef directly from slaughter or a variation on a theme of importing the entire cow for slaughter elsewhere (not technically Kobe, but close enough...)
After much research, I settled on 511 for their reputation of serving award winning Kobe beef (Grade A5 Beef Marbling Score 11 - hence the restaurant name) and also being one of the few that serves it as a kaiseki menu as well as the usual beef steak only option.
All guests other than us were Japanese, and my language skills (and their English skills) were not great in conveying which cuts of beef and added ingredients were being served. It didn't detract from an superlative meal.
The starter of seared Kobe beef with cod roe was a little teaser of the quality of beef and a salty roe kick to enhance the flavours. The 5 appetisers were from various parts of the cow, all nice but none particularly memorable. The chawanmushi was wonderful with uni (I adore good uni) above and tender beef underneath. The miso beef was reminiscent of Nobu's cod except with a heavier core. The monkfish was a refreshing break in between two beef courses, wedged on the other side by two beef sushi - one served with grated ginger and the other topped with salt.
We were then treated to an additional extra of Kobe beef jerky - salt cured and wetting appetites for the main attraction.
The A5 B11 Kobe sirloin was amazing. The proportion of fat is evident from the photos. Each slice was a melting flavour of beef and fat. It was unparalleled to any Wagyu beef I've previously tried all outside Japan - there is no competition. Sadly for me I paid a bit extra for the eye fillet, which had a much less percentage of fat (I read later this is expected given the different muscles areas) and was cooked more medium than my preferred rare.
Some rice and dessert dishes rounded up the meal but I remained transfixed on the beef that had just passed and contemplated whether to order any sirloin steak just to relive the experience. I refrained. I will go again.
Next time I would order the kaiseki menu again. The experience and variety is a much better overall dinner than I imagine a rich fatty steak alone. Choose sirloin, remember not to count calories and give thanks to the cows.
(Other places serve other cuts including rib-eye and chateaubriand - I'd be curious to know how their marbling compares with sirloin. If you only have one experience though, I'd definitely recommend sirloin for price and to know what you're getting.)