The game opens with high school student Aoi being "isekaied" into a fantasy world based on fairytales after following a black cat. Arriving in Wonderland (from "Alice in Wonderland"), Aoi is immediately attacked by robots who are erasing the storybook world. To escape, she becomes a giantess by eating the classic "Eat Me" cake and promptly destroys the robots.
After wandering Wonderland for a while, Aoi stumbles upon Alice, who's also a giantess, crushing some "dwarfs" (the world's average-sized inhabitants). Aoi fights and defeats Alice, after which she joins the party. Side note: Alice explains that crushing dwarfs doesn't actually kill them, just flatting them (cause fantasy world). Also, failing to defeat Alice will result in her using one of her abilities to increase in size and make Aoi into a pleasure toy.
After saving Wonderland, Aoi and Alice cross the sea, which only comes up to their knees, to Lilliput (the small country from "Gulliver's Travels"). Side note: the Lilliputians are normal sized here. After getting the typical Lilliput greeting, Aoi and Alice meet Gulliver, who's a natural giantess (no cake required) and has been gender-bend into a horny milf for some reason. After helping defend Lilliput from the robots, Gulliver joins the party, even using her tech-savviness to build a teleporter so they wouldn't have to cross the ocean all the time.
After traveling the continents for a while, the trio meet the mastermind behind the robots, Kaori; a novelist, and a former friend of Aoi until they had a fallout. When Aoi asked her why she, who always loved stories, would do something like this, Kaori reveals that, as a novelist, she can freely rewrite the fantasy world to suit her tastes, with both Alice and Gulliver having been altered by her. Also, the cat that initially brought Aoi to the fantasy world is revealed to be the main character from Kaori's original novel, having done so in hopes she would be able to stop its creator. Kaori then begins erasing the world around them, forcing Alice and Gulliver to take Aoi and flee with the teleporter.
Due to the teleporter malfunctioning, the trio to end up in Brobdingnag (the giant country from "Gulliver's Travels"); home to mega giantesses so huge Aoi and co. are dwarfs by comparison. The trio search for pieces to fix the teleporter while trying to not get crushed by the unaware Brobdingnagians. Failure will result in the trio becoming a "little" girl's pets.
After returning to the continent, and Aoi tripping over upon arriving at a place where she is a giantess again, the party once again confront Kaori. During the fight, Alice and Gulliver are infected by Kaori's corruption of the fantasy world, and they have a tearful goodbye with Aoi. After defeating Kaori, Aoi finally makes up with her. Failure will result in Kaori shrinking Aoi, Alice, and Gulliver into nothing.
Afterward, Aoi and Kaori return to their own world. However, Kaori forgot to turn them back to normal beforehand, causing them to make a BIG entrance. Also, Kaori uses her god-like power over the fantasy world to restore Alice and Gulliver as well as make a book titled "Grimm Glitter" that basically serves as a portal to allow them to visit them at any time.
After beating the main story, it's possible to unlock a few more (18+) CGs by fully leveling up all the characters, as well as fight a hidden boss; a Neko girl.