If you're wondering if you could ever play as Kaine in Nier Replicant, you'll find the answer in this guide, but be aware that what follows will contain major spoilers.
Can I play as Kaine in Nier Replicant?
In short, players can play as Kaine after seeing four of the first endings, including Ending D. That said, if you want to play as Kaine, you'll need to create a new game after completing the part where you need to. to erase you from existence to save Kaine. At this point, you'll need to create a new game and then play to the point where you fight Aerie's second boss.
Related: What Can I Sell in Nier Replicant?
After this fight, the game will put you in control of Kaine and you can play her for the rest of the area. However, this will be the only game you will have to play as her, and there is not an option where you can play as her for the rest of the game.
Still, that doesn't mean you can't have fun playing with her, as she has power abilities that can wreak havoc on shades. Along with that, she's super fast, and her abilities and movement speed seem to make up for her lack of magic spells.
For more on Nier Replicant, we at PGG highly recommend checking out How to Increase FPS on NieR Replicant on PC
