This setting is, frankly, pretty much lifted from Uru's game Size Matters. The world is exactly like our own in terms of technology; urban cities, electricity, phones, and so on. The main difference is that there's no men. At least, not as part of the dominant species. In essence, a race of giantesses have created this world and all of them are capable of some spell casting. They can shrink things, teleport things, scan for nearby signs of life, and move heavy objects. With alchemical potions, they can even make themselves multiply in size for a little while to be as big as a building or use a draught that will allow them to reproduce asexually. These giant women also have an inherent instinct that makes them want to toy with prey and squish them as their primary means of getting sexual pleasure, though some resist the urge because they think it's wrong or just plain unladylike. Some of the giantess race are even known to keep humans as pets. A life as a pet is humiliating and unenviable, but far from the worst fate that can befall you in this dystopia.

This is where humanity comes into play. Humans live in this same world, but are only a few inches tall. More accurately, the average giantess is about a hundred feet tall give or take. All human settlements have effectively been exterminated as the giantess race hunted them for sport and their own sadistic impulses. Now, humans have to live in hiding inside of giantess cities in order to find reliable sources of food, siphon electricity from their grid, and survive. Some businesses actually employ humans for certain types of work that you can do at any size or that they're better at but humans are often very wary of such offers. A promise of protection could merely be a trap resulting in one's untimely demise. Still, desperation and starvation often leads humans to eventually take them up on these offers and some are legitimate even though humans have no legal rights and their giantess employer could choose to do whatever they want with them. Public transportation has even added compartments for humans only where they're allegedly safe as long as they can pay the toll, but it's wise to doubt these. All too common is the story of the human comparment being breached and all the occupants tortured by whoever managed to unlock it before the driver noticed. Humans have formed settlements under appliances, inside sewers, and really anywhere that a giantess is unlikely to find them. Every now and then though, a city gets discovered by a giantess with too much free time on her hands and wiped out in minutes.

There is a human resistance, but most don't see a point to fighting back against such an utterly overwhelming foe. As it stands, a single giantess is practically invincible to the combined onslaught of the entire human race. Humans don't even remember a time where they were independent or free of these monsters, and so most don't even try to strike back. But that could all change with our hero...