Kōko's personality is very hard to explain because it usually always changes when it comes to Mitsuo Yanagisawa and later Banri Tada. For example, when she sees Mitsuo transfer to a new college, she hits him with a bouquet of red roses. When she is with Banri, she is really kind and honest and depends on him a lot. Due to Kōko's wealthy and rich family, she is raised with formal and strict ways of expression. This often makes her talk and behave quite differently compared to the other students. However, when she is with Banri she feels relaxed and calm, and doesn't hesitate to share her inner feelings with him. Despite being ditzy yet happy on the outside, she often feels lonely and unseen. Koko honestly wants to be a good girlfriend to Banri, but she doesn't know how to and hopes that she can improve simply because Banri is her first boyfriend. She is shown as a girl with devoted nature. Through out the series she pursues person of her affection single minded, which often gets to the point of stalking the person or being too clingy to them. She admits in front of Banri that she is aware that her this very nature seems to bother others, but she can't change herself. Kōko is also shown as a person with confidence when confessing her love and hold herself in high esteem for being a good girlfriend. However, she feels threatened / jealous whenever there is any girl around Mitsuo / Banri or someone takes care of Banri in her stead. And, she behaves rudely to them, such as her making fun of Chinami Oka. This feeling along with Banri's retro grade amnesia Kōko is always shown as an insecure lover. And time over time she tries to confirm feelings of Banri about her. However, as the time progress Kōko is convinced of Banri's feelings. After Banri shares his past with her she starts to help him face his problems and sort out his feelings. Overall she is shown as a person with a good nature, honest feelings, easy to be hurt and always tries to do her best for the person she loves. She is very pretty and nice to others.