Rewrite: Moon and Terra ending
I think that the 2nd season closed off with a good ending. My reasons for it is that Koutarou had the same relationship with the key by the complete end, but they all seemed to be back to how they normally were, school clothes and all the other things. I don't know why but I got the feeling they gasped not just because the two kissed, but because they knew the two of them so it was even more of a surprise.

A bad ending in my eyes would have kept him dressed in his butler suit and not have the scene where they look to be casually chatting while walking on the path of light on their way to the moon.