In many ways this is your archetypal slave training game - buy slaves, train them, fuck them, whore them out. Most of the basic mechanics are perfectly serviceable and reasonably well explained but not especially groundbreaking; the gameplay is fun and reasonably in depth but not mindblowing.
Where the game particular shines, somewhat ironically for a slave trainer game, is the writing and characters - every single slave has a personality and a wide variety of scenes unique to her, including special scenes as she falls for you and your relationship goes beyond master and slave; as affection and lewdness grow, they react to you talking to them differently and their expressions change too. Even the training scenes change significantly based on them being in heat or just really liking you; I personally didn't care for how rapey the initial scenes often are but after that it tends to be consensual. And there are A LOT of girls, I'd guesstimate around 20-30, so everything I said above is no joke in terms of content.
There are definitely some overlaps in training scenes (a lot of girls have some kind of blowjob scenes, about half the girls have a cowgirl scene, etc) but in general each girl is fun, unique, and likable, even most of the ones I didn't think I'd like. I was especially fond of the MILF ogre and the adorable (albeit slightly yandere) spider girl. Most of the scenes are pretty good too, though depending on your tastes you may or may not like some of the more hardcore ones like piss, egg laying, etc.
The plot is alright but not super special. You work for Millia, the blonde horned girl from the banner, because... some never really explained debt you owe her, and then when you pay it off she disappears and you never find out what her deal was. There are multiple endings, one for Millia, one for each slave, one for just running the brothel, and one for harem end.
While the actual prostitution bits are a bit underwhelming and repetitive (each girl only has 1 prostitution scene with variants), they can still be pretty hot and have enough depth to them that I found it an amusing minigame that didn't wear thin until around the end of my first playthrough, and then were fun again until around the end of my second playthrough.
Still, overall I greatly enjoyed the game; it's an unusual slave trainer game but one with a lot of heart to it, and I appreciate that. Probably more of a 4.5 than a perfect 5 but I highly recommend it nonetheless!