Mizuki Tachibana is a sixteen-year-old high school student and a close friend of Ryoko Kaminagi in the simulated world of Maihama. She is a member of the theatre club, tennis club, and volleyball team, reflecting her active and sociable nature. Her personality is straightforward and genuine, and she harbors a strong passion for acting. Mizuki initially has unrequited romantic feelings for Toya Hayase, fully aware that he is dating Sachiko Tsumura. Seeking closure, she confesses her feelings to him during the summer festival and is gently rejected. Later, she enters a happy relationship with Ushio, which continues until the server that contains their simulated world is reset. Mizuki does not awaken to the true nature of reality or become a Cerebrant pilot; her role in the story is that of a normal inhabitant of the simulation, serving as a supporting friend and a reminder of the ordinary life that the main characters are fighting to protect. Her favorite film is Last Year at Marienbad, a detail that hints at her contemplative side. She has no combat or special abilities, remaining a civilian character throughout the series. Her development centers on emotional growth, particularly moving on from her first love and finding contentment in a new relationship within the confines of her artificial world.