It's not the best trainer game I've ever played, but in Fantasy Trainer's defense, there's some stout competition. Fortunately, it's mostly forgettable issues. There's a handful of bugs and placeholder text that never got cleared out. In addition, the game doesn't feel quite finished despite it's tag. It takes just a little too long to reach new events with the girls.
On the down side, as seems to be typical with this genre, grind is an irritating issue. While they're not wildly original, they each have a distinct personality that generally feels worth seducing. The game is definitely worth a play due to the girls.
It's got decent writing, art which varies greatly in quality between good and awkward, and a good corruption arc for most of the girls. It's very representative of the genre, using a combination of conversations and sex acts to corrupt and/or romance the various girls. Fantasy Trainer is a typical trainer style game in which you flirt, tease, fuck and generally corrupt your way through a harem of about a half dozen girls.