I don't think it is an exaggeration to say that this game is the best adult game on the market. Actually I would go so far as to say it's the best RPG Maker game, period. And is certainly in contention to be one of the best made games of all time.
Everything about The Last Sovereign is a masterclass in its categories.
Writing
From world building, characterization, racial differences, tasteful smut and twists (actually engaging, well-established ones) that keep you on the edge of your seat at every moment.
The writing is so good, it actually inspired me to start writing myself. Opening my eyes to just what kind of emotionally-charged stories can be told about lust, jealousy, polygamy and love growing beyond our daily norms. Just incredible.
Gameplay
Most of the reviews go very in-depth in this regard, so I won't beat a dead horse. But if you love kingdom-building, actually meaningful decisions, being rewarded for thoroughness and meticulous decision-making. Then this game beats all contenders. Nothing comes even close to the depth and variability in the management aspect of this game, and that speaks nothing to the actual combat yet.
Combat is tough. Really. Especially later on. I am a resource hoarder in almost every game I play, with this one being the exception. Because Lustlord forbid you do not come in prepared for these fights with the right healing, magic and resistance potions. Truly engaging and tactical fights, without them being sadistic. Except the optional bosses...
Sex
This is an adult game, its why I first picked it up. To get my rocks off. And this game delivers beyond that. Honestly at the very beginning it feels very porn gamey, with the kind of circumstantial and kinky sex you'd see from other games in the genre, but with an incredible twist it immediately establishes that sex is more than that.
I got heart boners? Playing this game. Really. I loved every girl in the harem. Even those I thought were kind of throwaways to pump the numbers up I ended up really caring about. Which made the sex even hotter. And there are some real character beats delivered in these moments as well.
Rather than the MC having sex with 1000 girls 1 time. The roster is kept (relatively) small, but means that those girls all get more than one moment to shine. And you see their kinks, preferences and sexuality grow alongside every other part. Making for a depth of character that I I think isn't possible outside of stories that aren't willing to smut it up.
Conclusion
In conclusion. If you like games, and you like women. You should buy this immediately.