@purplelibraryguy
Yeah, a lot of this all goes hand in hand with Japanese culture. Since they're so very much a group mentality, being ostracized from the group is a bigger social horror than I think any westerner can truly appreciate. The Japanese are also all about not bothering people, especially with their personal problems, therefore that's why often kids never speak up about being bullied because it usually makes things worse anyway.
But again, manga is a form of media, and like all media, it's dramatized. So you also have to keep that in mind.
That being said, I gotta say I can relate hard core to "Japanese girl bullying". Girls from my own school did a lot of this mental warfare stuff I often read about in manga. The physical violence aspect was much less scarce, but whew lad. There was constant emotional/sociological warfare going on.