Which of the following is not a character in the video game Doki Doki Literature Club?

The answer is Nico because Nico is not a character in the video game Doki Doki Literature Club. The game features four main characters: Sayori, Natsuki, Yuri, and Monika. Each character plays a significant role in the game's narrative, while Nico is not mentioned or included as a character.