Well I can't say I have anything to do with the Japanese writing about 'Neo-Visual' bands, but I started using this term about 3 years ago specifically for the bands Girugamesh and Sadie which at the time were very new. While not exactly a genre, its more of a generation of bands. I'd say as a general rule of thumb (though not 100% of the time) Neo-Visual bands were formed after 2001.
If that is a bit vague, I will explain what Neo-Visual is REALLY supposed to mean: A generation of visual band, usually out of Tokyo, directly influenced by visual bands (indie and major) that came directly before them ~1996-1999. One quality many of these bands share is having more substance, full-bodied sound and often more bass driven than their predecessors. My favorite examples are bands like Dio and -Oz- and SKULL, but also refer to bands as far back as Kagerou, the Gazette and even Kagrra. Many people refer to Neo-Visual as 'New School Visual Kei"
For example think of the difference (or similarities) between Dir en grey from Kisou and Sadie. Of course half of the Japanese bands around today roadie'd for Dir en grey.. I think a great many of these bands were also took notes from whatever American hardcore and metal bands, trying to sound much more western than older visual bands.
Sorry I can't give you a simple answer for 'what is NeoVK?' but.. it's a very complex and amorphous place. ;D
