I like that title, goes very well with the Vanilla tag!
Hmm, I was almost expecting a story point where the spirits possess them, or that after what they did they were content and passed on or...Something like that.
I feel like that ending is supposed to kind of imply that? Well, it was still a nice and simple story overall, filled with sweet Vanilla loving and that's always nice.
Trusting that Keisuke-kun will "... Take Responsibility, Right?", ... or risk facing the unspeakable vengeance that only a father who's also a shrine's head priest can conjure up.
Or maybe even face the wrath of the god of the shrine they serve and work in. XD
Edit: After reading it. I think that either; A: they are the reborn spirits of those 2 from the past, or B: He is the reborn spirit and she is a ghost of the original girl. Thoughts and comments anyone?