I love tonkatsu!
Wako, Saboten, and Maisen are the three biggest tonkatsu chain restaurants. Their menus are priced pretty friendly, with often giving free refil of cabbage and rice! Their restaurants are in most of the major cities in Tokyo such as Shibuya, Shinjuku, and Ikebukuro. They also have combo menu which you will be able to other fried food.
Enjoy your tonkatsu!
I'd recommend Marugo in Akihabara. Their tonkatsu is juicy yet not oily and I think theirs are the best!