Looking at the date of this thread, it was 3 months ago when i began researching Visual Kei. Apparently, from the replies, except for a joker, no one expressed interest or even know or heard before this term.
Recently, I found that in this forum, there emerged a few people whom, I presume, are into Japanese Rock. Also, there seem to be some misunderstandings regarding Japanese Rock compared with other genre of music as well as artistes from other countries.
I hope by sharing some contents of my research paper about Visual Kei, you will grasp a better idea of this unique to Japan genre of music. (I prefer to call it a culture though)
Visual Kei's roots can be traced as far as the 16th-17th century. Since history, Japan is a culture vibrantly rich in song and dance. These 2 elements are everywhere and every time there is a festive season or a reason to celebrate. Japanese cultural performances are known as "Kabuki" (ge1 wu3 ji4), meaning song, dance and technique. However, Japan's society is very conservative and patriarchic, this led to the practice that women are not allowed to take part in open performances. When roles of women are to be portrayed, men will have to take on the task and cross-dress, often, with elaborate make-up and actions.
Visual Kei, is believed to be branched from Kabuki. Boys wearing loud costumes and make-up and get together to sing and dance. Gradually, they developed their own style and started making music underground. Visual Kei was not a mainstream culture as it connotates rebellious and breaking away from social norms. Performances took on a new form. The band would agree on a central theme, and prepare costumes and wrote music according to the theme. The costumes were often made by the members themselves, and the make-up too. The key point was that, their dressing is highly exaggerated, to create the "shocking" effect, also known as visual shock. Precisely, this is the essence of Visual Kei and fans are attracted to this rather than the music itself. Lyrics is not important. What matters most is the visual impact brought to the audience through the costume and the make-up.
Japanese rock fans can recall that in the 1980s, black lipstick and pink hair are symbolical of Japanese Rock. Sadly, it spells the death of the spirit of Visual Kei, but the birth of a modifed form of Visual Kei, which is known as Visual Rock. Dressing is no longer the crucial element. At this stage, bands put their attention into the music they create. Another interesting point is, bands began to promote the notion of assimilating their body-mind-soul into music, to the extend of extremism. An example will be, if the central theme is "Pain", the members will inflict pain on themselves, such as slashing their arms and scarification. Some people could not withstand the physical and emotional torture that they eventually left the bands. They also take a lot more pride in the instruments they play. Even when wearing heavy and elaborate costumes, they are still able to execute their forte. However, this also means that Visual Rock bands are getting on the mainstream track.
In the mid-1990s, we see a lot of Visual Rock bands toning down on their image. They discard the pink hair and black lipstick and bring on their instruments and vocals. The "visual" impact is almost gone, except for some hardcore bands like X-Japan and Gackt, who are still trying hard to maintain the Visual Rock image. Many bands "modernised", catering to mainstream audience, sheding off their gothic costumes and play music and sing at maximum decibels. Luna Sea is one of these bands that have betrayed Visual Rock.
It is believed that the misunderstanding that J-Rock imitates English Rock happened in this transitional period due to the similarities, especially in style. There may exist a grey area but they are starkly different in terms of roots and form.
The timeline will be something like this
Kabuki

Visual Kei

Visual Rock

Japanese Rock
It may seem that they are just different names for the same thing but each name represents a different period and form of Japanese Rock.
Music reflects a culture. Music is to be appreciated. Not to forget that, like any other thing, music is constantly undergoing metamorphism.
I'm not into Japanese Rock at all but i just happened to come across this little history when I was looking into Popular Culture in Japan. Seemed pretty cool and worth researching into. I looked at pictures of the bands then and now, watched their MTVs, clips of their concerts, read the official and fan sites. Of course there are more details and other sub-topics and issues along the way but this is a summary of the key contents.
Hope you have a better understanding of the term "Visual Kei" and Japanese Rock now.