[Kerberos]

I'm looking for help finding a mini-gts type story I can't remember the name of.

Basically the plot is about a guy and two girls. He finds some object (necklace I think) that lets him change reality and no one else notices. The most memorable scene I recall is the trio returning from a restaurant and as they go along he keeps making women he sees on the side walks, from the car he is in, taller, bustier, bigger etc. As he makes more and more and more women 7-8 foot tall giantesses eventually reality changes to cope with this that all women are that tall. The car he is in sizes up dramatically as this goes on.

Not sure where I read it, or the name, but that was a good one.