An athletic, beautiful, and popular girl in Masato's class. Although seemingly way out of his league, Masato begins dating her.
After some further investigating on Masato and Mizuki's half, they discover that Kaoru's name was on the list of students that were enrolled in the kindergarten that Yuki (and Masato for just one month) attended back in Shizuoka. Her name listed on the file was as "Kaoru Oozora," but her mother turned out to have remarried. Her name before the remarriage was "Kaoru Masato." She is the real "Maa-kun," and was mistaken by Yuki as being a boy due to her tomboyish appearance and behavior as a child.