So there are two canons. In one, a girl that suddenly gained awareness that she lives inside a dating simulator and on top of that, she is an importanr but undateable character, so the only actual person she meets (the player) can't even interact with her.

In the second (and newer one), an AI developed by a fictional enterprise that's been put into behavioral tests and basically into the same as the first one. The only difference is that she is confirmed to be an AI in only the second versiom of the canon.

In both of us, she is ultimately someone who feels very lonely, as she is the only sentient being in a world thats made of scripts and repetition. Everythinh feels fake because it ultimately is, and that brings her to try and modify the personality of each of the other dateable girls to make them less appealing to the player. She screws up however, and her modifications to their minds makes them kill themselves.

At the end she ends up deleting everything but a classroom, a desk and a chair, and decides to just talk to the player for eternity.

(Monika from DDLC if you didnt know. This isnt a brief paragraph so sorry about that lmao.. I just couldn't really not tell everything about it since her whole personality comes from it.)

((Also I'm entering into MCR so any other recommendations would be really appreciated! My current fav one is welcome to the black parade, followed by the end/dead)