Kōko is a freshman law student at Banri's university. She is extremely popular among boys, but has little to no friends, due to people being intimidated and scared to talk to her because of her beauty. To all appearances, she is the perfect lady. Since elementary school, she has been obsessed with Mitsuo, her childhood friend. In that time, she made a promise to marry Mitsuo, and ever since had been making her plans so that everything would come out perfect. However, she later falls in love with Banri and they start dating.