The main character of Doubt!. She was originally a 'jimi', the Japanese equivalent of a geek/nerd/dork, in junior high. After a devastating and embarrassing event she decides to step up her game. A few months before her first year of high school, she says she "manufactures" herself into a beautiful young woman. Now getting everyone's attention she enters a roller coaster of a ride in high school. The very first day of school she meets Sou Ichinose and his friend Yuichiro Kato, known as the two hottest guys in school. Mina Sato doesn't seem to be very happy with Ai after watching her hanging out with the boys too much. She becomes Ai's enemy for the first few chapters, thinking that Ai was trying to hook up with Yuichiro but after learning that she was actually after Sou, they become the best of friends. By the 2nd volume Ai and Sou enteres a relationship. But unfortunately for Ai, things go far from what she had expected when Yuichiro announces that he is in fact in love with her too.