First year high school girl Sawa Konishi transfers to Amabane High School, an escalator school, because she loves the school's cute uniforms. She doesn't realize that the school used to be an all-boys school, with this being the first year it has allowed girls. On the first day, she befriends Akira Nagashima, an aspiring manga artist. She also meets Ran Matsuyuki, the son of the school chairman, who kisses her on the forehead as a joke. As her day progresses, she learns most of the boys in the school don't listen to the teachers, following the lead of Ran.

Sawa's life in the academy is initially trouble, as she is bullied by the boys. At one point, they threw her shoes in the water and she nearly drowns trying to retrieve them. Ran unexpectedly saves her, causing Sawa to see him in a new light, and she eventually gains the respect from the rest of the boys. Ran also is interested in Sawa, and on his birthday, kisses her, leading to their dating. Ran's friend Junichi Tsubaki is one of the first to be aware of the new relationship. Having watched out for Ran since middle school, when Ran attempted to commit suicide, he is supportive of the relationship. Akira is initially upset by Sawa's new love, thinking Sawa will forget her, but Sawa helps her see that she values their friendship.

As Ran and Sawa continue their relationship, they encounter several trials where people try to break them up, including Kido and his sister Ayaka. However, when a popular movie star named Sugishita enrolls at Amabane High School, Sawa befriends him, unaware that the he is in love with her and sees Ran as a rival.