After Seeing the Comments, the Merman Hero Won Over the Villainess

Are There Any Stories Where a Merperson Falls in Love with the Female Lead and Sexually Differentiates into a Man?

Are there any stories where a mermaid falls in love with the female lead and undergoes gender differentiation to become male? I've been wanting to read something like this lately, but I haven't found anything similar. I remember seeing it in a quick transmigration story a long time ago, but I've forgotten the title.