The plot ? Well ... in big lines, shouldn't be hard to figure out
We have heard her dream - live happily with a loved one., and overcome her fear of men. (For the sake of that man, no doubt). Now, from the flashbacks it is clear she made a promise with a boy ... who is, no doubt, the one she was thinking of when telling her dream. Of course that boy is Shungo, only he has an amnesia like any proper male lead should.
I can already imagine that after a day gone wrong (more than usual) he would ask Mayu why she is trying so hard, then she would tell him about the promise she made with a boy back then, which would eventually get Shungo's gears turning and he would realize that she is the girl from that time... since from OP we know he can kiss her and is pretty much alive -> happily ever after ... But that is for later - i expect the majority to be fairly episodic and 'harmless fun'