I feel like a lot of people don’t understand why Caitlyn and Vi’s relationship works… Caitlyn loves Vi because Vi is a person that lives the way Cait wants and tries to live. All her life, Cait has tried to get away from the expectations that were placed on her just because she was born a Kiramman in Piltover. Vi is a person who had expectations placed on her just because she was born in Zaun, but she doesn’t follow those expectations. She does what she wants based on what she thinks is good and right and sticks to the “side” that has the same goal as her. That is what Cait wants and tries to be. She chose to be an enforcer because that’s where she believed she could do the most good. Then she chose to take on a more political role because she believed it would help her reach her goals. Cait and Vi don’t actually pick “sides”, they follow their moral compass, and Cait admires that in Vi.
Vi loves Cait BECAUSE Cait sees that in Vi. Vi really wants to be appreciated for what she does and the motives she has. She thrives when people tell her that they see that she has a good heart. It happened with Vander, and then with Cait. She tries so hard to do the right and the good thing and she wants and needs so badly for that to be seen. She knows that Cait is a good person because Cait sees that Vi tries, which to Vi must mean that Cait sees good vs. bad and right vs. wrong the same way she does.
They love each other because they are the only people left in their world who truly understand and see each other for who they really are and what they really believe in, in a world where most people care more about how pre-determined societal roles decide who you should be and what you should believe in. They both decided to be something else, and they love that about each other because, to them, a person like that is the best a person can be.