First of all, it's not a romance. Unless you think of an overly clingy little sister as romantic, I guess. There are no romantic feelings involved in neither side whatsoever.
Also, I wouldn't really consider it Harem. There are 2 girls clinging to him, which both are in some way (it's complicated) his sisters. That'd be a pretty small harem in my opinion.
So, if you want to watch this because you're looking for a harem/romance, you most likely won't be satisfied.
Considering the short duration of the show, the story was fine. As it also includes a supernatural aspect, some things are left unclear or simply have to be accepted 'as is' for it to work out. It's rather predictable, nothing mindblowing.
