Out of the giantesses world (early prototype)

This story will be about a guy who fell into the world of a giantesses against his will. This world is very similar to an ordinary human one. However, all technologies of that world are associated with magic. Every giantess can make a magic. But each giant girl needs an individual magic amplifier for the full use of her abilities. And this magical amplifier is a specially selected man from the human world. The main character of the novel is the guy who got into the world of giantesses instead of...