Magnets - Divine Blood Extracurricular

At age 16 in the Bravura Academy, Jeon Yoon-Ji is renowned as the top scorer of the school.  The vice president of the student council who is in charge of student discipline in many matters.  And she is regarded as the bad-ass wielder of the backscratcher of imminent beatdown.

But she wasn't always 16.

This takes place starting roughly 8 years before Divine Blood: Semester Start and advances to about 2 years before the novel.