 If you liked
Yumekui Merry
|
 ...then you might like
Hitoribocchi no Chikyuu Shinryaku
|
I got very similar vibes when reading both series. There is a boy and a girl, who are connected by what happened in their past, and the girl is not human. The past history is uncovered step-by-step and progressing the story. There are some fantasy fights too, and very slight romance undertones.