The Naiad’s Wish by Isabel Murray

Sayan never expected to fall for a human. He certainly never expected to bind himself to one, and yet that is exactly what he did.
He’d do it again.
Over and over again, he’d choose Erik.
But…
He just wished that Erik would stop leaving him, and going off to attend to his ‘responsibilities’ in the city.
If only Sayan could think of something to make him stay…

The Naiad’s Wish is an 11 000-word novelette about an insecure and possessive naiad and his patient human mate, with a minor tantrum, a joyful reunion, and more than a little bit of heat as Erik and Sayan smooth out a wrinkle or two in their new relationship.
This is best read after The Naiad’s Gift, book one in the Immortal Bonds series.