Hitched to the Wood Nymph by Eden Ember

In a world where humans are bound to monsters by fate, Acacia, a determined human, finds herself unexpectedly matched with Thornix, a mysterious wood nymph. As they navigate their forced union, they must confront the dark forces threatening their world and the forbidden love that blossoms between them.
In the harsh world of Magnus Terra, where humans live under the governance of monster districts, Acacia is matched with Thornix, a powerful wood nymph, through a DNA matching system designed to integrate humans and monsters. As they embark on their journey together, they face numerous challenges, including the societal pressures of their world and the internal conflicts of their own hearts. Through their struggles and discoveries, they must decide whether their bond can overcome the obstacles that threaten to tear them apart, or if it will become the very thing that saves them.

The Monster Matchmaking series is a spinoff of Arranged Monster Mates. Each book can be read as a stand-alone with a guaranteed HEA.
Tropes: Monster Romance, Science Fiction Romance, Fantasy Romance, Fantasy