From Okazu:

Hanaguchi Yoshiko is a transfer student into a high-end private school for girls. Like most of these in manga, it is an elevator school, so students that have been in the system from a younger age are given preference over outside students - and it is harder to transfer in at high school than middle school. Yoshiko is a writer - she even won a literature award as a young girl...a memory that haunts her to this day.

When she transfers into this garden of privilege, she basically ignores the crap the other girls pull on her, because she thinks they are a bunch of losers. She wears ear phones and writes and doesn't care if anyone likes her or not. When someone tries to bully her, she's right back in their faces, because she doesn't care. So of course, by her third year, she's the school hero. All the underclassman admire her brazen strength of will.

Yoshiko finds herself befriended by the star of the school, the impossibly rich, beautiful, perfect, popular, etc, etc, Takamiya Tsukiko. And then she finds herself being manipulated by two-faced Tsukiko. Yoshiko is not an idiot - she recognizes what's going on instantly. And then she does something I have never ever seen in a manga - she decides to let Tsukiko fuck with her, because she thinks it will make a great story.