Looking for an autobiographical work that was about a woman trying to get into artschool. ...

Looking for an autobiographical work that was about a woman trying to get into artschool. One of the main characters was her art teacher, and she kept bringing him up as if he'd died later on. I remember a specific scene where she's solving her mock exams using a coin and she gets 80% so he calls her a genius.
The author made a SUPER popular shojo manga before but I can't remember for the life of me who it was or which manga she wrote. TiA!