Monika

Monika is noted by the other characters to be smart, beautiful, confident and athletic. She is not as talkative as the other girls, but this is implied to not be through choice. She always has a calm, gentle expression and is portrayed as mature and hard-working. 

Monika had previously been a part of the Debate Club but left due to all the inner politics and drama, highlighting a desire for order, freedom of topics and friendliness. The Literature Club, which she founded after leaving the Debate Club, is very important to her. She aspires for it to be a place to showcase and grow everyone's passion for literature. Monika openly displays care and concern for her club mates, praising each member's writing style and even comparing them to famous authors and poets. 
Starting from Act 2, she shows a much more manipulative personality. It is revealed that Monika was self-aware all along and resented from being made into a minor role. She becomes infatuated with the player and urges them to spend more time with her. Monika begins trying to dispose of her club mates so the player is forced to choose her, after her attempts to make the other girls unlikable fail. Her desire and ambition lead her to become obsessive in this goal, highlighted by the fact that all of her poems are about the player or her epiphany. 
Despite Monika's upbeat attitude in the Literature Club, it becomes increasingly obvious that she is really sad and lonely, as a result of being aware that her whole world is just a simulation; a simulation in which she can't even achieve what is considered "happiness" (i.e. having her route completed). She fixates on the player so much because they're the only "real" thing in her life. It also does not help that, whenever someone quits the game, Monika is trapped in a hellish void of noise, lights, colors, and screams and despite not even being able to form coherent thoughts, she remembers all of it whenever the player turns on the game again. 

Later in the game, the player will be able to read Monika's Talk where she talks directly to the player, instead of the protagonist. It is shown that nothing about Monika's apparent kindness and politeness is an act, and she even offers the player some genuinely good advice from time to time./

From url=http://doki-doki-literature-club.wikia.com/wiki/MonikaDDLC Wiki