um not exaqctly visual kei, but you can try Aya Hirano. She has quite a bit of rock in her stuff. She's quite fun!
also i bumped into this chick a while ago. She seems to be categorised as j-pop but i hear a lot of heavy e-guitars in her stuff.:
and this one is um, a band of the KERA model Akira, DISACODE. She's a chick in cross dressing. I'm not very much into her vocals but, i thought i'll throw them in here as well....
i know you only requested j-rock but if you don't know about this chick yet, even though she's been floating around, i suggest to check Amit (or as she is knows as Amei in a pop world). But she's chinese. I absolutely love her, even though i just discovered that chick. Her stuff is amazing. Especially newest album.
(this is actually a ~3min track on the album)