How about a group of class bullies who get transformed in a similar way to each other, fitting in with remarks they had earlier made. The 1st calling someone a boob, another a prick, and another a pussy.

Each of them has their torso shrunk and turned into the body part they used as an insult with only their head, hands and feet left attached to a normal sized breast, cock and balls, or a pussy depending on which of the three different girls it is, so it's their only feature.

I'd really hope that the girl who has her body turned into a breast really freaks out for a minute when she realises she has no real genitals left, especially if she's a bit of a slut normally.

The final spin given by the student who is following Karma could be that all of them have their mouths turned into assholes because that's what they have been behaving like and they are left with their minds intact to struggle to eke out an existence in Karma's realm to be used as playthings for the creatures that live there.

I'd especially love to see your take on the girls in an illustrated form!

I think it would be neat for Kimiko/Uriko that their mother would merge with them somehow. Perhaps ether the mother simply becomes a short tail-like penis. Or they merge with their mother, with Kimiko becoming a large vagina/penis with Uriko remaining as the behind.