This one has been driving me crazy all day. From what I remember it's about a couple in the past and the girl is told by a god (i forget if it's to have the god's child or just marry him or something?) and the guy objects, but the girl stops him, not wanting him to get hurt. She goes through a portal and a few weeks/months? later she comes back a different person. In the end either she kills herself, he dies or something and flashing forward to a later date where he is reincarnated or something and he wants revenge.

It's something like that, a lot of it may be wrong.

Any help would be great!

This kind of reminds me of Yaotsukumo, although I could be wrong?

It's not it (but I will be reading it, thank you lol), when I say past..I mean like ancient times or something.