The Witcher 3: Wild Hunt has a lot of "mature" situations where Geralt of Rivia leaves his instincts prevail upon reason, but technically fans have not appreciated the way some of the in-game romances have been handled throughout the game. This hasn't stopped CD Projekt RED from creating some new scenes in the Hearts of Stone DLC, where you can have a new romance culminating in a sexual relationship with an old female friend of Geralt.
Here's how you can deepen your relationship with Shani, a young field medic, whom can lead you to two different sex scenes depending on the way you seducted her in the add-on.
ROMANCE
Doing the Dead Man's Party quest, you'll attend a wedding where you'll receive a side quest called A Midnight Clear, requiring you to help improve Shani's mood. Use Witcher senses and your knowledge of her preferences thanks to her journal, then find an appropriate present to cheer her up and talk to her in a proper manner in order to get her mood better.
SEX SCENE
The Witcher 3: Hearts of Stone offers two slightly different sex scenes with Shani, and it is directly proportional to the present you (as Geralt) offer to her to improve her mood. The first sex scene will start if you offer Shani Rowan flower, and if you offer her booze, the second sex scene will start.