(Be sure not to overdo it.) If people know you are going through a style change beforehand, then they will not be as surprised as if they had no warning. Alternatively, change style after a long holiday. The time gap will make the switch more plausible. Again, start subtly before you go over-the-top.

Summary:
Start telling your friends about visual Kei music or talking more about the style. Once you have changed your look noticeably, do not immediately wear all the brightest neons, biggest dresses or most vinyl bondage gear that you own.