Ootori Sayumi

A classmate who is kind and caring to everyone.
Her public face is that of a girl who loves cute things, but behind the scenes she is a strategist who looks at things objectively, playing the role of the good student in order to act in the best possible way.
However, she is not a bad person, and due to her naturally kind nature she acts as the leader of everyone at the dorm.
The protagonist finds out her true personality, shares her secrets with her, and uses her in various ways.