I've only heard of GACKT when he did the opening for Kamen Rider Decade. The MV for that song was the most self absorbed thing I've ever seen, the camera is always rotating on him and not on the main star. Also it's filmed in super slo-mo for some reason.
He is also playing Riderman in the Kamen Rider Decade Movie: All Rider vs Great Shocker
Journey Through The Decade - GACKT
The Next Decade - GACKT (which has NOTHING to do with the movie it's supposed to be promoting, Now you can argue well, some stuff are like that, with animes and such. But the thing is that some animes [most] dont have the artist spefically write and sing the song for the show, it's usually something off of their album. But with Tokusatsu shows {Kamen Rider and Super Sentai} The songs are about the characters so yeah)