The manga is about a girl who travels back in time, the first and like second chapter is when she is still in the modern world. She falls in love with her brother (I think it was because they didn't grow up together and they met later, and she didn't know in the beginning that they were siblings). Then something happens and she tries to run away but travels back in time, then she becomes a warrior and meets a guy who she maybe falls in love with (she basically falls out of love with her brother because she time travels). The brother is not a big part of the story and I think he was only in the first chapters before she time travels but I could be wrong.
It's an older manga which I read in 2014 or somewhat at that time. The manga is black and white, some chapters are in colour of what I can remember.