Rio Tsukatsuki

Rio is the student council president of Millennium. Cold and calculating, she cares more about objective facts than emotions. She is at odds with Himari due to their contrasting personalities. Her nickname is "Big Sister." Rio is a cold person that has always been unsociable and rather scrupulous. She never lets emotions change her mind and always sticks to the facts. Her determination to identify and analyze potential threats to Millennium and Kivotos at large has led her to develop an extensive surveillance system as a result. This in turn has caused her to gain a terrifying reputation among Millennium's student body, which she personally ignores. Rio is also very determined when it comes to reaching her goals, even breaking the rules if she has to.