Still looking for this shoujo manga TT_TT

I asked this question 4 years ago and got no answers so here I am asking it again ╥﹏╥ pls help me find it

I read this when I was little and I would love to read it again. 
The main character has pink (or is it purple?) hair and her name is Seira. I think she enrolls in a boarding school but she got difficulties because the school was really strict and the lessons were too difficult for her, but she was really hardworking and studied really hard until she passed out during the test. 
I remember her eating tuna to help her get smarter lol
Of course there's romance too, it's a shoujo manga after all XD

That's all I can remember, I really hope I could find it again >< That manga really gave such an impression on me because it shows the harsh reality of being a student. It is a very, very old manga and I have trouble finding it