Well, that was a total mess.
The film starts with schoolgirls saying that two of their friends have been killed or something. You'll wonder if you started watching the wrong thing. It feels like a sequel to something you missed, or perhaps you accidentally skipped the film's first hour. Is this a flash-forward? I've seen the full film and even now I don't know. Four yakuza (?) appear, throw their weight around and get killed by a surprisingly hands-on ghost (Hikiko-san). She just seems like another person in the scene. She'll punch you to death, twist your head until it's facing backwards, tear off your genitals, etc.
Do we ever see any of these people again? Not sure. Probably Hikiko-san herself, but even there it's hard to be certain. I think she's being played by Asami, who's wonderful but here doesn't get any dialogue and is barely recognisable under the hair and make-up.
Later, we meet the unstable mother of a boy who committed suicide and his best friend who blames himself. There's a dramatic core to this story (i.e. bullying and death)... but that's conveyed through exposition, so we don't see it. Furthermore, the related characters we do see aren't important. The "revengers" of the title are three girls who know martial arts and go around beating up bullies... or at least that's their excuse. They'll even pulverise yakuza. If their latest victim offers them money, they'll cheerfully turn on the client who wanted him beaten up.
One boy kills another boy and the film sort of forgets about it. A girl beats up two teachers (possibly killing one of them?) and there's similarly no mention of that later, although admittedly the issue is muddled by flashbacks and non-linear storytelling. The plot's a blob of bullies, anti-bullies and "what the hell am I watching?" One girl throws acid in another girl's face, because of course all schoolgirls carry bottles of acid to be on the safe side. On the upside, though, there's an attempt at thematic coherence, with people who claim to be fighting bullies but go too far. This even fits Hikiko herself.
None of this is scary. It's too cartoonish for that, while the "ghost" seems so mundane that it's tempting to conclude that there's no supernatural element at all and it's all just a disguise with wigs, clothes and make-up. (In one case, that's sort of true.) Some of the gore is funny, but there's also throat-slashing that inflicts no visible injury. Some of the acting is laughable. The revengers themselves are memorable (albeit also unlikeable), but carving "pig" into a girl's forehead would surely be a step too far for people who claim to regard themselves as anti-bully. This was a straight-to-video movie, needless to say, although a couple of its cast have acted in other things and its director's made a surprising number of other films.
It's got energy, though. Can't take that away from it. Furthermore, the script's basic concepts are worthwhile and a complete rewrite from scratch could have taken this something good.