It is about this girl in university who crosses paths with a boy from her chilhood who was responsable for her being bullied in school. The boy falls in love with her, but she can not forgive him so she plans to get revenge so she mistreats him, but with time she startsvwarming up to him as he is clearly in love with her.

Kimi no Sei possibly? Hope that was what you were looking for.

It was! Thank you so much