Geralt's complicated relationship with Yennefer of Vengerberg is one of the fundamental plot threads in the story that launched The Witcher franchise. Those who read Andrzej Sapkowski's books before immersing themselves in the game world might have been a little confused about Yennefer's absence in the first two games. While she was mentioned on occasion, she didn't appear until The Witcher 3: Wild Hunt, when Geralt was forced to decide what their relationship meant to him.
Source：https://www.cbr.com/the-witcher-yennefer-geralt-history/
