[spoonybard]

I believe that the use of English in Japanese music, particularly J-Rock/J-Metal comes from the fact that the music they are playing has its roots in English, and it may be that they want to express something that they simply feel sounds better in English. It's their choice, really, but they are not the only ones that do this; Nightwish and Children of Bodom are Finnish bands, yet their lyrics are in English, and so are those of Arch Enemy who's members are Swedish, except for the vocalist, who is German.