It's losely based on one of the stand alone short stories from one of the Novels. It's set some time after he left Yennefer but I think before Wild Hunt.
he's not fucking Essi. which arguably the point of the story, which apparently netflix didn't get.
tl/dr for the story.
its a short short based on the Little mermaid. book title is "the little sacrifice."
its framed by Dandelion and Geralt meeting up with a female Bard Essi. she's a little sister to dandelion. shes in love with Geralt. Geralt like her, kisses her.. but.. shes not Yennifer. and he can not reciprocate. and his inability to even properly verbalize that causes more grief.