Reborn as a mermaid

In a far far away unknownst to anyone place existed a galactic which consisted of millions of planets and stars. And  in one of them existed life, laws and flora-fauna which is  totally different than in earth.
Natives called this planet, Drehiri, their home. It was fifteen times bigger than Earth.
There existed different kind of races including humans, monsters, animals, never seen plants and many many other things that can not be explained by physics.
This story about a mermaid's magival advantures.
In this story :
1. will be romance(r18 scenes)
2. She Will not be the strongest she Will have her flows, heartbroken moments, defeats, near death situations, will meet betrayals but going through that she will grow stronger
3. In this world no one's perfect. There will be a little lgbt
4. I want to write it as realistic as I can
About her character she 's not weak, smart and careful. She has some anti hero charecteristics.
5. Every charecter has their own story
Ther' s no such a things as totally Black and White
6. There's no system to help mc

And lastly I am writing this Novel purely as a hobby