Futoria: Land of Futanari

In Futoria's world, women can't safely breed with the wild futanari they depend on for reproduction, since the cum is precious precisely because it's dangerous. Ava, cast out of her city, ends up alone in the forest and discovers the one thing nobody else knows about her: she can have sex with the futas without any of the risk everyone else fears.

That's the whole setup. Exiled protagonist, forbidden safe harbor, a world that punishes everyone else for the thing she can do freely.

From there it's a sandbox built around that advantage. Ava works the forest, fights monster girls, and builds relationships with the futas she meets, with combat and management layered over the sex itself. Getting close enough to a futa opens up more than encounters, too, letting you customize her look, hair and makeup included, once the relationship reaches the right stage. The queen's off-limits for now, in case you were wondering.