I just watched Mai Usami in SNIS-051 (http://www.akiba-online.com/showthread.php?t=1263665&highlight=%2Asnis-051%2A) and is it juts me or does she look like Miku Takaoka?
I've checked online and cannot find any reference to Miku Takaoka switching to JAV but if it's not her, it must be a twin...