Natsumi is Yuusuke's classmate, whom he has a crush on. She is an athletic diver. She is often spied upon by Yuusuke and his classmates from a small window at the diving complex at their school. She has a serious personality.
She has a boyfriend named Kai, who wears glasses, and seems older then her. Kai was her brother's best friend, and ever since his death, she had substituted Kai as her brother. She has had encounters with an angel, her deceased brother Fuyuki, which is proven later to be Raphael at the very end of the series.
At the beginning she seems to dislike Yuusuke because she believes he is a pervert, but later begins to get attracted to him.
