The story doesn't necessarily have to be ending. What if Tsukasa getting taken back to the moon leads to a long battle arc for Nasa to bring her back a la Bleach/Naruto/[insert shonen manga here]?
F--- Kazuya. He said some pretty shitty, selfish words right there. At a time when he really needs to stop thinking about himself. AND he has the gall to think what he is doing is actually helping Chizuru? "Put yourself and your feelings first?" !
Remember that all of this started due to...