I was talking with someone in this thread about the mangaka Mizukami awhile back and they suggested Spirit Circle. I finally remembered to look it up and it's excellent. It's relatively short at 45 chapters but it's well work reading and very deep.
It's really impossible to sum up the story, as it gets quite complex, but it starts out when a new transfer student seemingly has a strong grudge against the protagonist even though he has never seen her before. The truth is that she remembers their past lives and that they've been perpetual enemies throughout history. In fact, the birthmark on his cheek is a curse from one of her past selves.
She forces him to relive those lives so that he will understand her hatred. In doing so, he experiences joy but also heartbreaking pain, all while struggling to retain his own identity in the present.
