No, it's not a Hentai video, but a U.K. band that a friend turned me on to. They're difficult to pigeonhole, the closest thing I could describe them to would be "The Alan Parsons Project" with an edge. Here's a sample...
http://www.youtube.com/watch?v=cDlGLLFuTyI
They've apparently been around since the 80's and I can't believe I haven't heard them before. So if your a fan of well done (and intricate) instrumentals, I highly recommend checking them out. Enjoy!