It annoys me a bit, btw, that Ken Ishii is shown with this "correct your tags" picture within my library. Spelling an artist in his correct romanized (look at his bloody homepage) form doesn't make it "wrong" and people should get used to have two different artist pages until last.fm is actually getting to melt them (which seemingly never happens).
last.fm is suggesting Ishii's name written in japanese letters. If you enabled romanizing on last.fm (which helps to get your last.fm library straight), the website displays all japanese names in their romanized form, but it still differentiates them. That's why it seems that last.fm suggests the same name it thinks to be misspelled.