Hmm how about...

A demon and angel fell in love. It was forbidden and so they were punished when they got caught. The punishment was they were to live as humans. They will be reincarnated time and time again until they find each other and fall in love again. The catch is one of them will change appearance and place of birth every reincarnation but retains their memory. However, the other one will retain their appearance and place of birth but forgets their lover every reincarnation..


Another one I can think is similar to the first scenario but both have their appearance. Although, only one of them remembers the other and he cannot say "I love you" to their lover who has the amnesia. They cannot write it to them or even explain why they can't. If they try to, it causes them great pain that renders them weak and almost fainting.


What do you think?