I get excited when it seems like last.fm is actually making progress, so I'm going to list here some artists in my library that are still split. (You can see I am terrible at tagging!!)
All you have to do is vote for the Japanese reading! It's already an option, so you don't have to hunt for it!
Cap to Bin
Gokujou Seitokai Shikkobu
Hashida Norihiko & Shuberts