Characters
Inspiration
http://giantesscity.com/forum/viewtopic.php?f=12&t=112554
Basic Story
Two sisters are telepathic.. one naughty, one nice. The story opens as they show up to a new high-school, after leaving the old one because of an incident stirred up by the naughty one. Behind the scenes, we see the conflict from the two of them, as the nice one tries to keep people protected from her evil sister, help her evil sister stop being so evil, and generally help people.
The two sisters are twins, but they don't at all seem it, the "evil" one gorgeous, while the nice one homely. It turns out this is a side-effect of their telepathic interactions, as strong fantasies literally bring on physical changes. Opening scenes hint at this, as the evil sister notices and encourages the mental desires new acquaintances have for her. In an obviously old routine, the nice sister prods her to stop, while the naughty sister prods the nice sister to stop pretending she is someone she is not, taking on their problems instead of their desires (suggesting the link with her homeyness). The naughty sister does agree to keep it under wraps, while also laughing about the terrible situation she caused at their previous school. (There is also suggestion that it's not the naughty sister's fault, that if she didn't try so hard, she'd be even more changed... which seems hard to believe.)
There is more mind-reading humor and levity. (gay boy, teen crush, test cheating, teacher humiliation)
It's all old-hat, until the naughty sister finds someone with an unusual (mini giantess) fetish. It's one of the few boys her nice-sister likes, and they meet when she brings him by their home. It starts out as just a lust fantasy. He's sitting down, looking up at her chest, lusting after her. She encourages his daydream, and he imagines her coming onto him. As typical, she watches him embarrassingly respond to the quasi-hallucination, not realizing he's imagining her as being taller than him, taller than she actually is. Before she's finished 'toying' with him, she's already grown two inches taller, though she doesn't realize it.
The rest of the story chronicles:
The good sister fighting to keep the boy for herself...
The sisters noticing her additional height..
The good sister trying to keep her from doing more of it. The girls 'fighting over' the boy, with some mental control.
The good sister trying to stop him from fantasizing his sister, eventually forcing him to think of her instead.. bringing on her own dramatic 'transformation', against her intention.... this lets him in on their secret.
The good sister dealing with being 'objectively harassed' now that she's gorgeous, and doing a bad job of discouraging even stronger fantasies... leading to comic "unwanted" gorgeous changes.. even taller, even bigger breasts. Some at the hands of her boyfriend. She storms away from him because he won't or can't stop his fantasy from changing her.
Finally the 'evil' girl helps her, by explaining how she channels their fantasies into directions which avoid this kind of physical change. After the two reconcile, she 'teaches' her sister how to better control it, and even reverse some of the changes a little.
She tries to use these techniques to allow her to see her boyfriend again, with help from her sister. While it seems to be working at first, because they encourage him to fantasize about having a 'normally hot' girlfriend on his arm at school...It ultimately fails spectacularly, as they are not at school, so he gets them both caught up in his own private mini-gts fantasy. The 'nice' girl tries to resist and ask for help, but her naughty sister does no such thing, enjoying and feeding into the transformation. Ultimately, his fantasy ends up having as much power over them as they have over him.