I was Japan recently and with how much I saved up, I ended up going to Pierre Gagnaire as my big meal in Tokyo. If I had more money, I would have gone to one of the fabulous sushi restaurants in Ginza. Nevertheless, I had to eat sushi in Japan. Near my hostel in Asakusa, Tokyo; I went to a nearby standing sushi bar called Maguro-Bito (Kaminari-mon Branch). Maguro-Bito is actually a famous chain of conveyor-belt sushi-ya but these branches of standing sushi bars under the same name could be privately owned as I asked on the Japan-guide.com forums (http://www.japan-guide.com/forum/quereadisplay.html?0+93361 ) After I ordered o-toro, the chef ends up pulling out this amazing-looking piece of well-marbled tuna and said it was kamatoro, the fatty part located around the collar. It was extremely delicious and the best piece of toro I've ever had, granted never being at one of the high end sushi restaurants in Tokyo. After researching from here: http://www.sushiencyclopedia.com/blog... I found out that this amazing part of the tuna was even rare in Japan. Therefore, if you arrive in Japan looking for sushi, especially in Tokyo, ask for the kamatoro!
Yes, 'kama toro' is rare, 3% of the tuna. It is rarely found as it will rotten quickly, so in the contrary 'kama-toro yaki(grilled)' is found easily in Izakaya !! Unfortunately, it is full of fibre(muscle), so the cuts have to be on the opposite of the fiber !! Too firm to be used by high end sushi !
I did appreciate also Maguro-Bito, in Okachinachi, the team changed two year ago, and they couldn't answer my questions about provenance. That is too bad !!