You should visit Marugo (丸五) in Akihabara! They had the thickest pork yet softest and juiciest ever. I always recommend Marugo to every one :)
However, you should expect to wait a while especially if it's weekend's busy hours.
My favorite Tonkatsu restaurant is Maisen. (http://mai-sen.com/) This Tonkatsu is so soft that it can be cut with chopsticks. Sources for Tonkatsu are also delicious. You can choose the kinds of pork. Hope you will like it.
My favourite restaurant is Saboten. You can find about 70 restaurants in Japan. Nice meat and we can get rice and cabbage salad as much as we want!! Please see the restaurant details here!! (I can’t reach an English site... but there is.) Bonne appétit :)