This has been bothering me for months that I couldn't remember the title of this!
It was a fantasy manga, not completely sure if it was shoujo but the art style was very shoujo-like.
The main protagonist is a boy but in the past life or something he was a girl, a princess (that used magic i think) named Veronica. He remembers his past life but none of his classmates who were also involved with Veronica remembers. (But they later start to remember, like who was on the same side as main protagonist and who wasn't, betrayals etc etc.)
I would really appreciate if you help me identify this one.

Bokura No Kiseki

OMG so quick thank you!!